Publications
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21.
PARIMI, PV; SRIKANTH, H; BAILLEUL, M; SRIDHAR, S
R. SURYANARAYANAN, L. PINSARD and A. REVCOLEVSCHI. Journal Article
In: Tc, vol. 200, no. 250, pp. 300, 2001.
@article{parimi2001r,
title = {R. SURYANARAYANAN, L. PINSARD and A. REVCOLEVSCHI.},
author = {PV PARIMI and H SRIKANTH and M BAILLEUL and S SRIDHAR},
year = {2001},
date = {2001-01-01},
journal = {Tc},
volume = {200},
number = {250},
pages = {300},
abstract = {A sensitive tunnel diode oscillator (TDO) operating at 4MHz is used to probe the dynamic response of La1− xSrxMnO3 single crystals for x= 0.125, 0.175, 0.28 and 0.33 doping. Systematics of the measured change in reactance (∆ X) as a function of temperature (30K< T< 320K) and DC magnetic field (0< H< 6kOe) reveal distinct temperature and field scales associated with the dynamic response of spin. It is notable that these features are far more striking than the corresponding features in static measurements. The results are discussed in the context of structural changes leading to polaron ordering.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
A sensitive tunnel diode oscillator (TDO) operating at 4MHz is used to probe the dynamic response of La1− xSrxMnO3 single crystals for x= 0.125, 0.175, 0.28 and 0.33 doping. Systematics of the measured change in reactance (∆ X) as a function of temperature (30K< T< 320K) and DC magnetic field (0< H< 6kOe) reveal distinct temperature and field scales associated with the dynamic response of spin. It is notable that these features are far more striking than the corresponding features in static measurements. The results are discussed in the context of structural changes leading to polaron ordering.
22.
Kusko, C; Zhai, Z; Markiewicz, RS; Sridhar, S
Anomalous Scattering Rate and Microwave Absorption in Bi2Sr2CaCu2O8+ $delta$ and YBa2Cu3O7- $delta$ Journal Article
In: Journal of superconductivity, vol. 14, no. 1, pp. 81–84, 2001.
@article{kusko2001anomalous,
title = {Anomalous Scattering Rate and Microwave Absorption in Bi2Sr2CaCu2O8+ $delta$ and YBa2Cu3O7- $delta$},
author = {C Kusko and Z Zhai and RS Markiewicz and S Sridhar},
year = {2001},
date = {2001-01-01},
journal = {Journal of superconductivity},
volume = {14},
number = {1},
pages = {81--84},
publisher = {Kluwer Academic Publishers-Plenum Publishers},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
23.
Dresselhaus, MS; Oates, D; Sridhar, S
Studies of High-T sub c Superconducting Films for High-Power Microwave Applications Technical Report
DTIC Document 2001.
@techreport{dresselhaus2001studies,
title = {Studies of High-T sub c Superconducting Films for High-Power Microwave Applications},
author = {MS Dresselhaus and D Oates and S Sridhar},
year = {2001},
date = {2001-01-01},
institution = {DTIC Document},
abstract = {During the period of this grant, October 15, 1997-April 14, 2001, characterization has been carried out in order to understand microwave properties of grain boundaries. Measurements in an externally applied dc magnetic field in addition to the rf field of the stripline resonator. Intermodulation distortion measurements have also been carried out as a function of the grain boundary angle. The measurements in external magnetic fields require the use of a suspended micros trip geometry without superconductivity ground planes so that the shielding effects of the ground planes could be avoided. The film parameters which give the best device characterization have been established.},
keywords = {},
pubstate = {published},
tppubtype = {techreport}
}
During the period of this grant, October 15, 1997-April 14, 2001, characterization has been carried out in order to understand microwave properties of grain boundaries. Measurements in an externally applied dc magnetic field in addition to the rf field of the stripline resonator. Intermodulation distortion measurements have also been carried out as a function of the grain boundary angle. The measurements in external magnetic fields require the use of a suspended micros trip geometry without superconductivity ground planes so that the shielding effects of the ground planes could be avoided. The film parameters which give the best device characterization have been established.
24.
Parimi, PV; Hakim, N; Chou, FC; Cheong, SW; Sridhar, S
Dielectric signatures of lattice instabilities at 32K and 245K in $ La_ $$2-y$$ Sr_ $$y$$ MO_ $$4+ x$$ $(M= Cu, Ni) Cuprates and Nickelates Journal Article
In: arXiv preprint cond-mat/0108342, 2001.
@article{parimi2001dielectric,
title = {Dielectric signatures of lattice instabilities at 32K and 245K in $ La_ $$2-y$$ Sr_ $$y$$ MO_ $$4+ x$$ $(M= Cu, Ni) Cuprates and Nickelates},
author = {PV Parimi and N Hakim and FC Chou and SW Cheong and S Sridhar},
year = {2001},
date = {2001-01-01},
journal = {arXiv preprint cond-mat/0108342},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
25.
Parimi, Patanjali; Zhai, Zhiyong; Hakim, Nazih; Kusko, Christian; Sridhar, Srinivas; Amerahl, Udo; Vietkine, A; Revcolevschi, A
Charge Polarization Dynamics of Spin-Ladder and Spin-Chain Sr-Cu-O Cuprates. Proceedings Article
In: APS Meeting Abstracts, 2000.
@inproceedings{parimi2000charge,
title = {Charge Polarization Dynamics of Spin-Ladder and Spin-Chain Sr-Cu-O Cuprates.},
author = {Patanjali Parimi and Zhiyong Zhai and Nazih Hakim and Christian Kusko and Srinivas Sridhar and Udo Amerahl and A Vietkine and A Revcolevschi},
year = {2000},
date = {2000-01-01},
booktitle = {APS Meeting Abstracts},
abstract = {Single crystals of spin-ladder and spin-chain cuprates, Sr-Cu-O, revealed novel features in the temperature dependence of microwave dielectric susceptibility, ε= ε'+ iε", carried out in a highly sensitive a superconducting microwave cavity. The results show new dynamic phenomena due to dielectric relaxation with time scales corresponding to GHz frequency range. For spin-ladder Sr_14-xCa_xCu_24O_41 with x= 0 we have observed loss peak with a pronounced frequency dependence in the ε"(omega, T) response around 200K accompanied by a rapid decrease in ε'(omega, T). The frequency dependence of this phenomenon can be understood by considering a complex dielectric constant ε= ε 0/(1-i omega tau). Doping dependence of ε (omega, T) for x= 2, 8, 11.5 showed a shift in the peak to lower temperatures. The microscopic origin of this phenomenon can be understood by comparing the ε (omega, T) of …},
keywords = {},
pubstate = {published},
tppubtype = {inproceedings}
}
Single crystals of spin-ladder and spin-chain cuprates, Sr-Cu-O, revealed novel features in the temperature dependence of microwave dielectric susceptibility, ε= ε'+ iε", carried out in a highly sensitive a superconducting microwave cavity. The results show new dynamic phenomena due to dielectric relaxation with time scales corresponding to GHz frequency range. For spin-ladder Sr_14-xCa_xCu_24O_41 with x= 0 we have observed loss peak with a pronounced frequency dependence in the ε"(omega, T) response around 200K accompanied by a rapid decrease in ε'(omega, T). The frequency dependence of this phenomenon can be understood by considering a complex dielectric constant ε= ε 0/(1-i omega tau). Doping dependence of ε (omega, T) for x= 2, 8, 11.5 showed a shift in the peak to lower temperatures. The microscopic origin of this phenomenon can be understood by comparing the ε (omega, T) of …
26.
Xin, H; Oates, DE; Sridhar, S; Dresselhaus, G; Dresselhaus, MS
RAPID COMMUNICATIONS-Superfluidity and superconductivity-Observation of individual Josephson vortices in YBa2Cu3O7-d bicrystal grain-boundary junctions Journal Article
In: Physical Review-Section B-Condensed Matter, vol. 61, no. 22, pp. R14952, 2000.
@article{xin2000rapid,
title = {RAPID COMMUNICATIONS-Superfluidity and superconductivity-Observation of individual Josephson vortices in YBa2Cu3O7-d bicrystal grain-boundary junctions},
author = {H Xin and DE Oates and S Sridhar and G Dresselhaus and MS Dresselhaus},
year = {2000},
date = {2000-01-01},
journal = {Physical Review-Section B-Condensed Matter},
volume = {61},
number = {22},
pages = {R14952},
publisher = {Woodbury, NY: published by the American Physical Society through the~…},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
27.
Zhai, Z; Kusko, C; Hakim, N; Sridhar, S; Revcolevschi, A; Vietkine, A
Precision microwave dielectric and magnetic susceptibility measurements of correlated electronic materials using superconducting cavities Journal Article
In: Review of Scientific Instruments, vol. 71, no. 8, pp. 3151–3160, 2000.
@article{zhai2000precision,
title = {Precision microwave dielectric and magnetic susceptibility measurements of correlated electronic materials using superconducting cavities},
author = {Z Zhai and C Kusko and N Hakim and S Sridhar and A Revcolevschi and A Vietkine},
year = {2000},
date = {2000-01-01},
journal = {Review of Scientific Instruments},
volume = {71},
number = {8},
pages = {3151--3160},
publisher = {American Institute of Physics},
abstract = {We analyze microwave cavity perturbation methods, and show that the technique is an excellent, precision method to study the dynamic magnetic and dielectric response in the GHz frequency range. Using superconducting cavities, we obtain exceptionally high precision and sensitivity for measurements of relative changes. A dynamic electromagnetic susceptibility ζ̃(T)=ζ′+iζ″ is introduced, which is obtained from the measured parameters: the shift of cavity resonant frequency δf and quality factor Q. We focus on the case of a spherical sample placed at the center of a cylindrical cavity resonant in the TE011 mode. Depending on the sample characteristics, the magnetic permeability μ̃, the dielectric permittivity ε̃=ε′+iε″, and the complex conductivity σ̃=σ′+iσ″ can be extracted from ζ̃H. A full spherical wave analysis of the cavity perturbation indicates that: (i) In highly insulating samples with dielectric constant ε′∼1, the measured ζ̃H∼χ̃M, enabling direct measurement of the magnetic susceptibility. The sensitivity of the method equals or surpasses that of dc superconducting quantum interference device measurements for the relative changes in magnetic susceptibility. (ii) For moderate ε̃ and conductivity σ̃, ζ̃H∝ε̃+iωσ̃/ε0−1, thus enabling direct measurement of the sample dielectric constant ε̃, even though the sample is placed in a microwave magnetic field. (iii) For large σ we recover the surface impedance limit. (iv) Expressions are provided for the general case of a lossy dielectric represented by ε̃+iωσ̃/ε0. We show that an inversion procedure can be used to obtain ε̃+iωσ̃/ε0 in a wide range of parameter values. This analysis has led to the observation of new phenomena in novel low-dimensional materials. We discuss results on magneto dynamics of the three-dimensional (3D) antiferromagnetic state of the spin chain compound Sr2CuO3. In dielectric susceptibility measurements in Sr14Cu24O41, we directly observe a dielectric loss peak. Dimensional resonances in the paraelectric material SrTiO3 are shown to occur due to the rapid increase of dielectric constant with decreasing temperature. The cavity perturbation methods are thus an extremely sensitive probe of charge and spin dynamics in electronic materials.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
We analyze microwave cavity perturbation methods, and show that the technique is an excellent, precision method to study the dynamic magnetic and dielectric response in the GHz frequency range. Using superconducting cavities, we obtain exceptionally high precision and sensitivity for measurements of relative changes. A dynamic electromagnetic susceptibility ζ̃(T)=ζ′+iζ″ is introduced, which is obtained from the measured parameters: the shift of cavity resonant frequency δf and quality factor Q. We focus on the case of a spherical sample placed at the center of a cylindrical cavity resonant in the TE011 mode. Depending on the sample characteristics, the magnetic permeability μ̃, the dielectric permittivity ε̃=ε′+iε″, and the complex conductivity σ̃=σ′+iσ″ can be extracted from ζ̃H. A full spherical wave analysis of the cavity perturbation indicates that: (i) In highly insulating samples with dielectric constant ε′∼1, the measured ζ̃H∼χ̃M, enabling direct measurement of the magnetic susceptibility. The sensitivity of the method equals or surpasses that of dc superconducting quantum interference device measurements for the relative changes in magnetic susceptibility. (ii) For moderate ε̃ and conductivity σ̃, ζ̃H∝ε̃+iωσ̃/ε0−1, thus enabling direct measurement of the sample dielectric constant ε̃, even though the sample is placed in a microwave magnetic field. (iii) For large σ we recover the surface impedance limit. (iv) Expressions are provided for the general case of a lossy dielectric represented by ε̃+iωσ̃/ε0. We show that an inversion procedure can be used to obtain ε̃+iωσ̃/ε0 in a wide range of parameter values. This analysis has led to the observation of new phenomena in novel low-dimensional materials. We discuss results on magneto dynamics of the three-dimensional (3D) antiferromagnetic state of the spin chain compound Sr2CuO3. In dielectric susceptibility measurements in Sr14Cu24O41, we directly observe a dielectric loss peak. Dimensional resonances in the paraelectric material SrTiO3 are shown to occur due to the rapid increase of dielectric constant with decreasing temperature. The cavity perturbation methods are thus an extremely sensitive probe of charge and spin dynamics in electronic materials.
28.
Xin, Hao; Oates, DE; Sridhar, S; Dresselhaus, G; Dresselhaus, MS
Observation of individual Josephson vortices in YBa 2 Cu 3 O 7- $delta$ bicrystal grain-boundary junctions Journal Article
In: Physical Review B, vol. 61, no. 22, pp. R14952, 2000.
@article{xin2000observation,
title = {Observation of individual Josephson vortices in YBa 2 Cu 3 O 7- $delta$ bicrystal grain-boundary junctions},
author = {Hao Xin and DE Oates and S Sridhar and G Dresselhaus and MS Dresselhaus},
year = {2000},
date = {2000-01-01},
journal = {Physical Review B},
volume = {61},
number = {22},
pages = {R14952},
publisher = {American Physical Society},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
29.
Zhai, Z; Parimi, Patanjali V; Sridhar, S
Erratum: Nonlinear microwave impedance of short and long Josephson junctions [Phys. Rev. B 59, 9573 (1999)] Journal Article
In: Physical Review B, vol. 62, no. 17, pp. 11888, 2000.
@article{zhai2000erratum,
title = {Erratum: Nonlinear microwave impedance of short and long Josephson junctions [Phys. Rev. B 59, 9573 (1999)]},
author = {Z Zhai and Patanjali V Parimi and S Sridhar},
year = {2000},
date = {2000-01-01},
journal = {Physical Review B},
volume = {62},
number = {17},
pages = {11888},
publisher = {APS},
abstract = {The discussion of the resistively-shunted Josephson junction ~RSJ! model starts with the second paragraph of section
‘‘V. REMARKS’’ on page 9578 of our paper. Throughout this section the remarks that were made pertain to the analysis
where the RSJ model was used. Careful reading of our paper reveals that the reference 17 ~Portis et al.! was cited in the
context of the modulated microwave absorption experiments only. We were not referring to the model analysis carried out in
the papers cited ~Ref. 17!. Since no analysis was done in the paper by Portis et al. in terms of RSJ, it is clear that the
subsequent discussion in our paragraph does not refer to or criticize the model analysis that Portis et al. have carried out in
their paper. Instead the discussion refers to an RSJ model description of such experiments if one were to calculate dc
quantities, rather than ac quantities, which are more appropriate, as is done in our paper. We acknowledge V. V. Srinivasu for
requesting a clarification on this issue.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
The discussion of the resistively-shunted Josephson junction ~RSJ! model starts with the second paragraph of section
‘‘V. REMARKS’’ on page 9578 of our paper. Throughout this section the remarks that were made pertain to the analysis
where the RSJ model was used. Careful reading of our paper reveals that the reference 17 ~Portis et al.! was cited in the
context of the modulated microwave absorption experiments only. We were not referring to the model analysis carried out in
the papers cited ~Ref. 17!. Since no analysis was done in the paper by Portis et al. in terms of RSJ, it is clear that the
subsequent discussion in our paragraph does not refer to or criticize the model analysis that Portis et al. have carried out in
their paper. Instead the discussion refers to an RSJ model description of such experiments if one were to calculate dc
quantities, rather than ac quantities, which are more appropriate, as is done in our paper. We acknowledge V. V. Srinivasu for
requesting a clarification on this issue.
‘‘V. REMARKS’’ on page 9578 of our paper. Throughout this section the remarks that were made pertain to the analysis
where the RSJ model was used. Careful reading of our paper reveals that the reference 17 ~Portis et al.! was cited in the
context of the modulated microwave absorption experiments only. We were not referring to the model analysis carried out in
the papers cited ~Ref. 17!. Since no analysis was done in the paper by Portis et al. in terms of RSJ, it is clear that the
subsequent discussion in our paragraph does not refer to or criticize the model analysis that Portis et al. have carried out in
their paper. Instead the discussion refers to an RSJ model description of such experiments if one were to calculate dc
quantities, rather than ac quantities, which are more appropriate, as is done in our paper. We acknowledge V. V. Srinivasu for
requesting a clarification on this issue.
30.
Sridhar, S; Giannakopoulos, AE; Suresh, S
STRUCTURAL, MECHANICAL, THERMODYNAMIC, AND OPTICAL PROPERTIES OF CONDENSED MATTER (PACS 61-68, 78)-Mechanical and electrical responses of piezoelectric solids to conical indentation Journal Article
In: Journal of Applied Physics, vol. 87, no. 12, pp. 8451–8456, 2000.
@article{sridhar2000structural,
title = {STRUCTURAL, MECHANICAL, THERMODYNAMIC, AND OPTICAL PROPERTIES OF CONDENSED MATTER (PACS 61-68, 78)-Mechanical and electrical responses of piezoelectric solids to conical indentation},
author = {S Sridhar and AE Giannakopoulos and S Suresh},
year = {2000},
date = {2000-01-01},
journal = {Journal of Applied Physics},
volume = {87},
number = {12},
pages = {8451--8456},
publisher = {New York, NY: American Institute of Physics, c1937-},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
31.
Sridhar, S; Zhai, Z
Non-quasiparticle microwave absorption in Bi2Sr2CaCu2O8+ $delta$ Journal Article
In: Physica C: Superconductivity, vol. 341, pp. 2057–2060, 2000.
@article{sridhar2000non,
title = {Non-quasiparticle microwave absorption in Bi2Sr2CaCu2O8+ $delta$},
author = {S Sridhar and Z Zhai},
year = {2000},
date = {2000-01-01},
journal = {Physica C: Superconductivity},
volume = {341},
pages = {2057--2060},
publisher = {North-Holland},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
32.
Sridhar, S; Zhai, Z; Parimi, PV; Hakim, N
Microwave Absorption Peaks: Signatures of Charge Dynamics in Cuprate Superconductors Proceedings Article
In: APS Meeting Abstracts, 2000.
@inproceedings{sridhar2000microwave,
title = {Microwave Absorption Peaks: Signatures of Charge Dynamics in Cuprate Superconductors},
author = {S Sridhar and Z Zhai and PV Parimi and N Hakim},
year = {2000},
date = {2000-01-01},
urldate = {2000-01-01},
booktitle = {APS Meeting Abstracts},
keywords = {},
pubstate = {published},
tppubtype = {inproceedings}
}
33.
Parimi, PV; Srikanth, H; Bailleul, M; Sridhar, S; Suryanarayanan, R; Pinsard, L; Revcolevschi, A
rf Susceptibility of La 1- x Sr x MnO 3 Single Crystals: Magnetic Signatures of Structural Changes Journal Article
In: MRS Online Proceedings Library Archive, vol. 602, 1999.
@article{parimi1999rf,
title = {rf Susceptibility of La 1- x Sr x MnO 3 Single Crystals: Magnetic Signatures of Structural Changes},
author = {PV Parimi and H Srikanth and M Bailleul and S Sridhar and R Suryanarayanan and L Pinsard and A Revcolevschi},
year = {1999},
date = {1999-01-01},
journal = {MRS Online Proceedings Library Archive},
volume = {602},
publisher = {Cambridge University Press},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
34.
Dasgupta, T; Choudhury, Durga P; Sridhar, S
Modeling nonlinearity and hysteresis due to critical-state flux penetration in hard superconductors Journal Article
In: arXiv preprint cond-mat/9905063, 1999.
@article{dasgupta1999modeling,
title = {Modeling nonlinearity and hysteresis due to critical-state flux penetration in hard superconductors},
author = {T Dasgupta and Durga P Choudhury and S Sridhar},
year = {1999},
date = {1999-01-01},
journal = {arXiv preprint cond-mat/9905063},
abstract = {The nonlinear surface impedance of a thin superconducting strip carrying a microwave current has been calculated numerically from first principles based upon flux penetration due to a current-induced critical state. The calculations approach analytic results in the appropriate limit. The technique is useful for design of passive superconducting microwave circuits.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
The nonlinear surface impedance of a thin superconducting strip carrying a microwave current has been calculated numerically from first principles based upon flux penetration due to a current-induced critical state. The calculations approach analytic results in the appropriate limit. The technique is useful for design of passive superconducting microwave circuits.
35.
Patanjali, PV; Theule, P; Zhai, Z; Hakim, N; Sridhar, S; Suryanarayanan, R; Apostu, M; Dhalenne, G; Revcolevschi, A
High-frequency magnetoimpedance of double perovskite La 1.2 Sr 1.8 Mn 2 O 7: Secondary transitions at high temperatures Journal Article
In: Physical Review B, vol. 60, no. 13, pp. 9268, 1999.
@article{patanjali1999high,
title = {High-frequency magnetoimpedance of double perovskite La 1.2 Sr 1.8 Mn 2 O 7: Secondary transitions at high temperatures},
author = {PV Patanjali and P Theule and Z Zhai and N Hakim and S Sridhar and R Suryanarayanan and M Apostu and G Dhalenne and A Revcolevschi},
year = {1999},
date = {1999-01-01},
journal = {Physical Review B},
volume = {60},
number = {13},
pages = {9268},
publisher = {American Physical Society},
abstract = {The nonlinear dependence on applied ac field
(
b
ω
)
or current
(
i
ω
)
of the microwave (ac) impedance
R
ω
+
i
X
ω
of both short and long Josephson junctions is calculated under a variety of excitation conditions. The dependence on the junction width is studied, for both field symmetric (current antisymmetric) and field antisymmetric (current symmetric) excitation configurations. The resistance shows steplike features every time a fluxon (soliton) enters the junction, with a corresponding phase slip seen in the reactance. For finite widths the interference of fluxons leads to some interesting effects which are described. Many of these calculated results are observed in microwave impedance measurements on intrinsic and fabricated Josephson junctions in the high temperature superconductors. When a dc field
(
b
dc
)
or current
(
i
dc
)
is applied, interesting phase locking effects are observed in the ac impedance
Z
ω
.
In particular an almost periodic dependence on the dc bias is seen similar to that observed in microwave experiments at very low dc field bias. These results are generic to all systems with a
cos
(
φ
)
potential in the overdamped limit and subjected to an ac drive.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
The nonlinear dependence on applied ac field
(
b
ω
)
or current
(
i
ω
)
of the microwave (ac) impedance
R
ω
+
i
X
ω
of both short and long Josephson junctions is calculated under a variety of excitation conditions. The dependence on the junction width is studied, for both field symmetric (current antisymmetric) and field antisymmetric (current symmetric) excitation configurations. The resistance shows steplike features every time a fluxon (soliton) enters the junction, with a corresponding phase slip seen in the reactance. For finite widths the interference of fluxons leads to some interesting effects which are described. Many of these calculated results are observed in microwave impedance measurements on intrinsic and fabricated Josephson junctions in the high temperature superconductors. When a dc field
(
b
dc
)
or current
(
i
dc
)
is applied, interesting phase locking effects are observed in the ac impedance
Z
ω
.
In particular an almost periodic dependence on the dc bias is seen similar to that observed in microwave experiments at very low dc field bias. These results are generic to all systems with a
cos
(
φ
)
potential in the overdamped limit and subjected to an ac drive.
(
b
ω
)
or current
(
i
ω
)
of the microwave (ac) impedance
R
ω
+
i
X
ω
of both short and long Josephson junctions is calculated under a variety of excitation conditions. The dependence on the junction width is studied, for both field symmetric (current antisymmetric) and field antisymmetric (current symmetric) excitation configurations. The resistance shows steplike features every time a fluxon (soliton) enters the junction, with a corresponding phase slip seen in the reactance. For finite widths the interference of fluxons leads to some interesting effects which are described. Many of these calculated results are observed in microwave impedance measurements on intrinsic and fabricated Josephson junctions in the high temperature superconductors. When a dc field
(
b
dc
)
or current
(
i
dc
)
is applied, interesting phase locking effects are observed in the ac impedance
Z
ω
.
In particular an almost periodic dependence on the dc bias is seen similar to that observed in microwave experiments at very low dc field bias. These results are generic to all systems with a
cos
(
φ
)
potential in the overdamped limit and subjected to an ac drive.
36.
Zhai, Z; Patanjali, PV; Hakim, N; Sokoloff, JB; Sridhar, S; Ammerahl, U; Vietkine, A; Revcolevschi, A
Observation of spin freezing and relaxation at microwave frequencies in the spin ladder compound $ Sr_ $$14-x$$ Ca_ $$x$$ Cu_ $$24$$ O_ $$41$$ $ Journal Article
In: arXiv preprint cond-mat/9903198, 1999.
@article{zhai1999observation,
title = {Observation of spin freezing and relaxation at microwave frequencies in the spin ladder compound $ Sr_ $$14-x$$ Ca_ $$x$$ Cu_ $$24$$ O_ $$41$$ $},
author = {Z Zhai and PV Patanjali and N Hakim and JB Sokoloff and S Sridhar and U Ammerahl and A Vietkine and A Revcolevschi},
year = {1999},
date = {1999-01-01},
journal = {arXiv preprint cond-mat/9903198},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
37.
Sridhar, S; Zhai, Z; Erb, A
Microwave Absorption Peaks: Signatures of Spin Dynamics in Cuprates Journal Article
In: arXiv preprint cond-mat/9906053, 1999.
@article{sridhar1999microwave,
title = {Microwave Absorption Peaks: Signatures of Spin Dynamics in Cuprates},
author = {S Sridhar and Z Zhai and A Erb},
year = {1999},
date = {1999-01-01},
journal = {arXiv preprint cond-mat/9906053},
abstract = {We show that a common feature of temperature-dependent microwave absorption is the presence of absorption peaks. ac loss peaks can arise when the internal T-dependent magnetic relaxation time crosses the measurement frequency. These features are observed in the QTR{em}{insulating} (SrxCa14−xCu24O41, La5/3Sr1/3NiO4 and YBa2Cu3O6.0), QTR{em}{pseudo-gap} (T>Tc in underdoped YBa2Cu3O7−δ, Hg:1223 and Hg:1201) and QTR{em}{superconducting} (T<Tc) states of the oxides. The commonality of these features suggests a magnetic (spin) mechanism, rather than a quasiparticle origin, for the so-called ``conductivity'' peaks observed in the cuprate superconductors.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
We show that a common feature of temperature-dependent microwave absorption is the presence of absorption peaks. ac loss peaks can arise when the internal T-dependent magnetic relaxation time crosses the measurement frequency. These features are observed in the QTR{em}{insulating} (SrxCa14−xCu24O41, La5/3Sr1/3NiO4 and YBa2Cu3O6.0), QTR{em}{pseudo-gap} (T>Tc in underdoped YBa2Cu3O7−δ, Hg:1223 and Hg:1201) and QTR{em}{superconducting} (T<Tc) states of the oxides. The commonality of these features suggests a magnetic (spin) mechanism, rather than a quasiparticle origin, for the so-called ``conductivity'' peaks observed in the cuprate superconductors.
38.
Choudhury, Durga P; Derov, John S; Sridhar, S
Harmonic generation from YBCO microwave resonators Journal Article
In: arXiv preprint cond-mat/9904080, 1999.
@article{choudhury1999harmonic,
title = {Harmonic generation from YBCO microwave resonators},
author = {Durga P Choudhury and John S Derov and S Sridhar},
year = {1999},
date = {1999-01-01},
journal = {arXiv preprint cond-mat/9904080},
abstract = {Measurement of harmonic power on a suspended stripline microwave resonator patterned out of thin film YBa_2Cu_3O_7 (YBCO) has been carried out as a function of temperature and microwave power. The third harmonic power P_3 shows a subtle nonlinear dependence on the fundamental power P_1 on a log-log scale. Fit to a straight line yields slopes of P_3 vs. P_1 between 1.5 to 3, contrary to elementary calculations that predict a slope of exactly 3. It is shown that third harmonic power generated from higher order terms in the nonlinear impedance could account for the discrepancy quantitatively without resorting to any additional ad-hoc assumptions. Results of measurement of fifth harmonic power is presented as a confirmation. A small second harmonic power is also observed that does not show anomalous power dependence within the experimental accuracy.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Measurement of harmonic power on a suspended stripline microwave resonator patterned out of thin film YBa_2Cu_3O_7 (YBCO) has been carried out as a function of temperature and microwave power. The third harmonic power P_3 shows a subtle nonlinear dependence on the fundamental power P_1 on a log-log scale. Fit to a straight line yields slopes of P_3 vs. P_1 between 1.5 to 3, contrary to elementary calculations that predict a slope of exactly 3. It is shown that third harmonic power generated from higher order terms in the nonlinear impedance could account for the discrepancy quantitatively without resorting to any additional ad-hoc assumptions. Results of measurement of fifth harmonic power is presented as a confirmation. A small second harmonic power is also observed that does not show anomalous power dependence within the experimental accuracy.
39.
Zhai, Z; Parimi, Patanjali V; Sridhar, S
Nonlinear microwave impedance of short and long Josephson junctions Journal Article
In: Physical Review B, vol. 59, no. 14, pp. 9573, 1999.
@article{zhai1999nonlinear,
title = {Nonlinear microwave impedance of short and long Josephson junctions},
author = {Z Zhai and Patanjali V Parimi and S Sridhar},
year = {1999},
date = {1999-01-01},
journal = {Physical Review B},
volume = {59},
number = {14},
pages = {9573},
publisher = {APS},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
40.
Kidambi, V; Zhai, Z; Srikanth, H; Sridhar, S; Erb, A; Li, Qiang
Vortex response of YBCO and BSCCO single crystals from RF experiments Proceedings Article
In: APS March Meeting Abstracts, 1998.
@inproceedings{kidambi1998vortex,
title = {Vortex response of YBCO and BSCCO single crystals from RF experiments},
author = {V Kidambi and Z Zhai and H Srikanth and S Sridhar and A Erb and Qiang Li},
year = {1998},
date = {1998-01-01},
booktitle = {APS March Meeting Abstracts},
abstract = {We have studied the mixed state radio-frequency (RF) response of YBCO and BSCCO cuprate single crystals over a wide range in temperature (4K < T < T_c) and DC magnetic fields (0 < H < 7T). The crystals are mounted inside an inductive coil and a sensitive resonance technique is employed to detect changes in the RF inductance of the samples. This is related to the penetration depth in the superconducting state and for fields exceeding the lower critical field, H_c1, reflects the dynamic response of the vortices to the oscillating RF signal. In both YBCO and BSCCO, our data reveal several characteristic field scales and variations associated with flux entry and dynamics. A systematic mapping of these field scales in the (H-T) plane will be presented. Standard issues related to the nature of the flux lattice in YBCO and BSCCO like pinning, surface barrier effects, "fishtail" anomalies and melting of the vortex lattice will be examined in the context of our results.},
keywords = {},
pubstate = {published},
tppubtype = {inproceedings}
}
We have studied the mixed state radio-frequency (RF) response of YBCO and BSCCO cuprate single crystals over a wide range in temperature (4K < T < T_c) and DC magnetic fields (0 < H < 7T). The crystals are mounted inside an inductive coil and a sensitive resonance technique is employed to detect changes in the RF inductance of the samples. This is related to the penetration depth in the superconducting state and for fields exceeding the lower critical field, H_c1, reflects the dynamic response of the vortices to the oscillating RF signal. In both YBCO and BSCCO, our data reveal several characteristic field scales and variations associated with flux entry and dynamics. A systematic mapping of these field scales in the (H-T) plane will be presented. Standard issues related to the nature of the flux lattice in YBCO and BSCCO like pinning, surface barrier effects, "fishtail" anomalies and melting of the vortex lattice will be examined in the context of our results.
1997
78.
Pance, K; Zhai, Zhiyong; Srikanth, H; Sridhar, S; Erb, A; Walker, E; Flukiger, R
Microwave response in ultrapure YBa_2Cu_3O_7-x single crystals grown in BaZrO3 crucibles: Effect of oxygen doping Proceedings Article
In: APS March Meeting Abstracts, 1997.
Abstract | BibTeX | Tags: Superconductivity
@inproceedings{pance1997microwave,
title = {Microwave response in ultrapure YBa_2Cu_3O_7-x single crystals grown in BaZrO3 crucibles: Effect of oxygen doping},
author = {K Pance and Zhiyong Zhai and H Srikanth and S Sridhar and A Erb and E Walker and R Flukiger},
year = {1997},
date = {1997-01-01},
booktitle = {APS March Meeting Abstracts},
abstract = {Recent progress in the growth of YBa_2Cu_3O_7-x single crystals using BaZrO 3 crucibles has opened up the possibility of studying the intrinsic properties of cuprates with great precision. We present complex surface impedance measurements on optimally oxygenated (x= 0.05, T_c= 93.4 K) and fully oxygenated (x= 0.0, T_c= 88.2 K) single crystals grown in BaZrO 3 crucibles. The real and imaginary parts of the microwave conductivity (sigma_1-i sigma_2) reveal features associated with two superconducting components. Enhanced pair conductivity is seen below about 65K and in addition to the normal conductivity peak at 40K, a second peak around 80K is also seen in these crystals. Systematic investigation of these new features in a number of crystals are reported as the growth conditions as well as oxygenation are varied. While the new features in sigma 1 and sigma 2 persist in the fully oxygenated crystals …},
keywords = {Superconductivity},
pubstate = {published},
tppubtype = {inproceedings}
}
Recent progress in the growth of YBa_2Cu_3O_7-x single crystals using BaZrO 3 crucibles has opened up the possibility of studying the intrinsic properties of cuprates with great precision. We present complex surface impedance measurements on optimally oxygenated (x= 0.05, T_c= 93.4 K) and fully oxygenated (x= 0.0, T_c= 88.2 K) single crystals grown in BaZrO 3 crucibles. The real and imaginary parts of the microwave conductivity (sigma_1-i sigma_2) reveal features associated with two superconducting components. Enhanced pair conductivity is seen below about 65K and in addition to the normal conductivity peak at 40K, a second peak around 80K is also seen in these crystals. Systematic investigation of these new features in a number of crystals are reported as the growth conditions as well as oxygenation are varied. While the new features in sigma 1 and sigma 2 persist in the fully oxygenated crystals …
77.
Choudhury, Durga P; Willemsen, Balam A; Derov, John S; Sridhar, S
Nonlinear response of HTSC thin film microwave resonators in an applied DC magnetic field Journal Article
In: IEEE transactions on applied superconductivity, vol. 7, no. 2, pp. 1260–1263, 1997.
Abstract | BibTeX | Tags: Superconductivity
@article{choudhury1997nonlinear,
title = {Nonlinear response of HTSC thin film microwave resonators in an applied DC magnetic field},
author = {Durga P Choudhury and Balam A Willemsen and John S Derov and S Sridhar},
year = {1997},
date = {1997-01-01},
journal = {IEEE transactions on applied superconductivity},
volume = {7},
number = {2},
pages = {1260--1263},
publisher = {IEEE},
abstract = {The non-linear microwave surface impedance, Z/sub s/=R/sub s/+iX/sub s/, of patterned YBCO thin films, was measured using a suspended line resonator in the presence of a perpendicular DC magnetic field, H/sub DC/, of magnitude comparable to that of the microwave field, H/sub rf/. Signature of the virgin state was found to be absent even for relatively low microwave power levels. The microwave loss was initially found to decrease for small applied H/sub DC/ before increasing again. Also, non-linearities inherent in the sample were found to be substantially suppressed at low powers at these applied fields. These two features together can lead to significant improvement in device performance.},
keywords = {Superconductivity},
pubstate = {published},
tppubtype = {article}
}
The non-linear microwave surface impedance, Z/sub s/=R/sub s/+iX/sub s/, of patterned YBCO thin films, was measured using a suspended line resonator in the presence of a perpendicular DC magnetic field, H/sub DC/, of magnitude comparable to that of the microwave field, H/sub rf/. Signature of the virgin state was found to be absent even for relatively low microwave power levels. The microwave loss was initially found to decrease for small applied H/sub DC/ before increasing again. Also, non-linearities inherent in the sample were found to be substantially suppressed at low powers at these applied fields. These two features together can lead to significant improvement in device performance.
76.
Willemsen, Balam A; Derov, JS; Sridhar, S
Critical-state flux penetration and linear microwave vortex response in YBa 2 Cu 3 O 7- $delta$ films Journal Article
In: Physical Review B, vol. 56, no. 18, pp. 11989, 1997.
BibTeX | Tags: Superconductivity
@article{willemsen1997critical,
title = {Critical-state flux penetration and linear microwave vortex response in YBa 2 Cu 3 O 7- $delta$ films},
author = {Balam A Willemsen and JS Derov and S Sridhar},
year = {1997},
date = {1997-01-01},
journal = {Physical Review B},
volume = {56},
number = {18},
pages = {11989},
publisher = {American Physical Society},
keywords = {Superconductivity},
pubstate = {published},
tppubtype = {article}
}
75.
Srikanth, H; Sridhar, S; Gajewski, DA; Maple, MB
Microwave properties of (PrxY1- x) Ba2Cu3O7- $delta$: influence of magnetic scattering Journal Article
In: Physica C: Superconductivity, vol. 291, no. 3-4, pp. 235–241, 1997.
BibTeX | Tags: Superconductivity
@article{srikanth1997microwaveb,
title = {Microwave properties of (PrxY1- x) Ba2Cu3O7- $delta$: influence of magnetic scattering},
author = {H Srikanth and S Sridhar and DA Gajewski and MB Maple},
year = {1997},
date = {1997-01-01},
journal = {Physica C: Superconductivity},
volume = {291},
number = {3-4},
pages = {235--241},
publisher = {North-Holland},
keywords = {Superconductivity},
pubstate = {published},
tppubtype = {article}
}
74.
Zhai, Z; Srikanth, H; Sridhar, S; Erb, A; Walker, E; Flukiger, R
Observation of coherent Josephson response in the non-linear ab-plane microwave impedance of Y Ba2Cu3O6. 95 single crystals Journal Article
In: Physica C: Superconductivity, vol. 282, pp. 1601–1602, 1997.
Abstract | BibTeX | Tags: Superconductivity
@article{zhai1997observation,
title = {Observation of coherent Josephson response in the non-linear ab-plane microwave impedance of Y Ba2Cu3O6. 95 single crystals},
author = {Z Zhai and H Srikanth and S Sridhar and A Erb and E Walker and R Flukiger},
year = {1997},
date = {1997-01-01},
journal = {Physica C: Superconductivity},
volume = {282},
pages = {1601--1602},
publisher = {North-Holland},
abstract = {We report novel non-linear phenomena in the ab-plane microwave impedance of Y BaCu2O7−δ single crystals. The Rs vs. Hrf data are well described by the non-linear RSJ model: φ + sin φ = irf cosωt. The entire crystal behaves like a single Josephson junction. The extraordinary coherence of the data suggests an intrinsic mechanism.},
keywords = {Superconductivity},
pubstate = {published},
tppubtype = {article}
}
We report novel non-linear phenomena in the ab-plane microwave impedance of Y BaCu2O7−δ single crystals. The Rs vs. Hrf data are well described by the non-linear RSJ model: φ + sin φ = irf cosωt. The entire crystal behaves like a single Josephson junction. The extraordinary coherence of the data suggests an intrinsic mechanism.
73.
Sridhar, S; Srikanth, H; Zhai, Z; Willemsen, BA; Jacobs, T; Erb, A; Walker, E; Flukiger, R
Evidence for multi-component superconducting order parameter from microwave measurements of YBa2Cu3O7- $delta$ single crystals Journal Article
In: Physica C: Superconductivity, vol. 282, pp. 256–259, 1997.
BibTeX | Tags: Superconductivity
@article{sridhar1997evidence,
title = {Evidence for multi-component superconducting order parameter from microwave measurements of YBa2Cu3O7- $delta$ single crystals},
author = {S Sridhar and H Srikanth and Z Zhai and BA Willemsen and T Jacobs and A Erb and E Walker and R Flukiger},
year = {1997},
date = {1997-01-01},
journal = {Physica C: Superconductivity},
volume = {282},
pages = {256--259},
publisher = {North-Holland},
keywords = {Superconductivity},
pubstate = {published},
tppubtype = {article}
}
72.
Willemsen, BA; Derov, JS; Sridhar, S
Critical-state flux penetration and linear microwave vortex response in YBa $$sub 2$$ Cu $$sub 3$$ O $$sub 7 $$minus$$$$delta$$$$ films Journal Article
In: Physical Review, B: Condensed Matter, vol. 56, no. 18, 1997.
BibTeX | Tags: Superconductivity
@article{willemsen1997criticalb,
title = {Critical-state flux penetration and linear microwave vortex response in YBa $$sub 2$$ Cu $$sub 3$$ O $$sub 7 $$minus$$$$delta$$$$ films},
author = {BA Willemsen and JS Derov and S Sridhar},
year = {1997},
date = {1997-01-01},
journal = {Physical Review, B: Condensed Matter},
volume = {56},
number = {18},
keywords = {Superconductivity},
pubstate = {published},
tppubtype = {article}
}
71.
Sridhar, S
Microwave conductivity of ultrapure YBa_2Cu_3O_7-delta single crystals: Evidence for a two-component order parameter Proceedings Article
In: APS March Meeting Abstracts, 1997.
Abstract | BibTeX | Tags: Superconductivity
@inproceedings{sridhar1997microwave,
title = {Microwave conductivity of ultrapure YBa_2Cu_3O_7-delta single crystals: Evidence for a two-component order parameter},
author = {S Sridhar},
year = {1997},
date = {1997-01-01},
booktitle = {APS March Meeting Abstracts},
abstract = {New features are reported in precision measurements of the complex microwave conductivity of ultra-pure YBa_2Cu_3O_6. 95 crystals grown in BaZrO 3 crucibles. Additional pairing is seen developing at around 65K and a second normal conductivity peak is observed at around 80K. The data are inconsistent with a single d-wave order parameter, and instead are indicative of two superconducting components. Overall, these results point to the presence of multiple pairing interactions in YBa_2Cu_3O_6. 95 and provide an explanation of the experimentally observed microwave conductivity peaks. The role of impurities and Oxygen doping will be discussed. We also report novel non-linear phenomena in the microwave impedance of the single crystals. The non-lin ear impedance data are well described by considering the equation for the phase of a resistively shunted Josephson junction: dotphi+ sin phi= i_rfcos …},
keywords = {Superconductivity},
pubstate = {published},
tppubtype = {inproceedings}
}
New features are reported in precision measurements of the complex microwave conductivity of ultra-pure YBa_2Cu_3O_6. 95 crystals grown in BaZrO 3 crucibles. Additional pairing is seen developing at around 65K and a second normal conductivity peak is observed at around 80K. The data are inconsistent with a single d-wave order parameter, and instead are indicative of two superconducting components. Overall, these results point to the presence of multiple pairing interactions in YBa_2Cu_3O_6. 95 and provide an explanation of the experimentally observed microwave conductivity peaks. The role of impurities and Oxygen doping will be discussed. We also report novel non-linear phenomena in the microwave impedance of the single crystals. The non-lin ear impedance data are well described by considering the equation for the phase of a resistively shunted Josephson junction: dotphi+ sin phi= i_rfcos …
70.
Choudhury, Durga P; Willemsen, Balam A; Derov, John S; Sridhar, S
Measurement of Microwave Magnetic Hysteresis of Thin Film HTSC and Comparison with a Modified Critical State Model Proceedings Article
In: APS March Meeting Abstracts, 1997.
Abstract | BibTeX | Tags: Superconductivity
@inproceedings{choudhury1997measurement,
title = {Measurement of Microwave Magnetic Hysteresis of Thin Film HTSC and Comparison with a Modified Critical State Model},
author = {Durga P Choudhury and Balam A Willemsen and John S Derov and S Sridhar},
year = {1997},
date = {1997-01-01},
booktitle = {APS March Meeting Abstracts},
abstract = {The hysteretic flux density B(H) of thin film HTSC resonators is measured through <A HREF=http://sagar.physics.neu.edu/preprints.html>measurements of microwave surface impedance</A> Z_s(H,T). A modified critical state model is examined to explain the data. The model generalizes Bean's original proposition by (i)including the demagnetization effects of perpendicular geometry which is commonly employed in experiments, (ii) including more than one critical currents as would be expected to exist in thin films and polycrystals, and (iii) generalizing the hysteresis law that is generally ascribed to this case. All this is done while still retaining the fundamental notions of a critical state. Our model shows good agreement with characteristic features of the data. Experimentally observed novel effects when the microwave and the DC fields are of comparable magnitude are also described. Implications of our experiment towards harmonic generation and intermods will also be presented.
},
keywords = {Superconductivity},
pubstate = {published},
tppubtype = {inproceedings}
}
The hysteretic flux density B(H) of thin film HTSC resonators is measured through <A HREF=http://sagar.physics.neu.edu/preprints.html>measurements of microwave surface impedance</A> Z_s(H,T). A modified critical state model is examined to explain the data. The model generalizes Bean's original proposition by (i)including the demagnetization effects of perpendicular geometry which is commonly employed in experiments, (ii) including more than one critical currents as would be expected to exist in thin films and polycrystals, and (iii) generalizing the hysteresis law that is generally ascribed to this case. All this is done while still retaining the fundamental notions of a critical state. Our model shows good agreement with characteristic features of the data. Experimentally observed novel effects when the microwave and the DC fields are of comparable magnitude are also described. Implications of our experiment towards harmonic generation and intermods will also be presented.
69.
Zhai, Zhiyong; Srikanth, H; Sridhar, S; Erb, A
Novel non-linear intrinsic Josephson response of YBa_2Cu_3O_7-delta single crystals Proceedings Article
In: APS March Meeting Abstracts, 1997.
Abstract | BibTeX | Tags: Superconductivity
@inproceedings{zhai1997novel,
title = {Novel non-linear intrinsic Josephson response of YBa_2Cu_3O_7-delta single crystals},
author = {Zhiyong Zhai and H Srikanth and S Sridhar and A Erb},
year = {1997},
date = {1997-01-01},
booktitle = {APS March Meeting Abstracts},
abstract = {Novel non-linear phenomena in the microwave impedance of ultra-pure YBCO single crystals are reported. The non-linear surface impedance Zs as a function of the microwave field strength H_rf is extracted using a procedure which affords quantitative analysis from non-Lorentzian resonances of high-Q resonators. The data show the presence of a threshold rf field followed by a parabolic rise of the surface resistance modulated by a step-like structure as a function of H_rf. The overall features can be well described by the dissipative and reactive response of an overdamped Josephson equation of the general form : φ'+sinφ = i_rfcosωt. It would require a unique intrinsic phase variable or an extremely coherent array of JJs or weak links to account for this phenomenon. Models based on the short and long junction limits and possible mechanisms which lead to the observation of this unique effect will be presented.},
keywords = {Superconductivity},
pubstate = {published},
tppubtype = {inproceedings}
}
Novel non-linear phenomena in the microwave impedance of ultra-pure YBCO single crystals are reported. The non-linear surface impedance Zs as a function of the microwave field strength H_rf is extracted using a procedure which affords quantitative analysis from non-Lorentzian resonances of high-Q resonators. The data show the presence of a threshold rf field followed by a parabolic rise of the surface resistance modulated by a step-like structure as a function of H_rf. The overall features can be well described by the dissipative and reactive response of an overdamped Josephson equation of the general form : φ'+sinφ = i_rfcosωt. It would require a unique intrinsic phase variable or an extremely coherent array of JJs or weak links to account for this phenomenon. Models based on the short and long junction limits and possible mechanisms which lead to the observation of this unique effect will be presented.
1996
68.
Choudhury, DP; Oxx, S; Jacobs, T; Srikanth, H; Willemsen, Balam A; Sridhar, S; Cho, BK; Canfield, PC
Interplay of Magnetism and Superconductivity n the Radio Frequency Response of Borocarbide Superconductors. Proceedings Article
In: APS March Meeting Abstracts, 1996.
Abstract | BibTeX | Tags: Superconductivity
@inproceedings{choudhury1996interplay,
title = {Interplay of Magnetism and Superconductivity n the Radio Frequency Response of Borocarbide Superconductors.},
author = {DP Choudhury and S Oxx and T Jacobs and H Srikanth and Balam A Willemsen and S Sridhar and BK Cho and PC Canfield},
year = {1996},
date = {1996-01-01},
booktitle = {APS March Meeting Abstracts},
abstract = {The electrodynamic response of single crystals of the borocarbide supercondctors LnNi_2B_2C where Ln= Y, Lu, Tm, Er, Ho, Dy has been studied as a function of temperature and applied magnetic field. An ultra stable tunnel diode oscillator set-up was used to determine Deltalambda (T, H, theta) at 3 MHz. In the Ho compound the onset of antiferromagnetic order below T c is observed as a significant reduction in the superconducting order parameter. Structure is observed in the angular dependence both above and below T_N, which cannot be fully explained with simple anisotropy of H_c2. In the Dy compound the magnetic ordering is evident in the T dependence of the normal state skin depth (ie in the scattering of the normal state carriers). Further structure in the magnetic state is revealed in experiments where H is varied at fixed T. Work at NU supported by the NSF through NSF-DMR-9223850 and Rome …},
keywords = {Superconductivity},
pubstate = {published},
tppubtype = {inproceedings}
}
The electrodynamic response of single crystals of the borocarbide supercondctors LnNi_2B_2C where Ln= Y, Lu, Tm, Er, Ho, Dy has been studied as a function of temperature and applied magnetic field. An ultra stable tunnel diode oscillator set-up was used to determine Deltalambda (T, H, theta) at 3 MHz. In the Ho compound the onset of antiferromagnetic order below T c is observed as a significant reduction in the superconducting order parameter. Structure is observed in the angular dependence both above and below T_N, which cannot be fully explained with simple anisotropy of H_c2. In the Dy compound the magnetic ordering is evident in the T dependence of the normal state skin depth (ie in the scattering of the normal state carriers). Further structure in the magnetic state is revealed in experiments where H is varied at fixed T. Work at NU supported by the NSF through NSF-DMR-9223850 and Rome …
67.
Oxx, S; Choudhury, DP; Willemsen, Balam A; Srikanth, H; Sridhar, S; Cho, BK; Canfield, PC
Vortex response and critical fields observed via RF penetration depth measurements on the superconductor YNi2B2C Journal Article
In: Physica C: Superconductivity, vol. 264, no. 1-2, pp. 103–108, 1996.
Abstract | BibTeX | Tags: Superconductivity
@article{oxx1996vortex,
title = {Vortex response and critical fields observed via RF penetration depth measurements on the superconductor YNi2B2C},
author = {S Oxx and DP Choudhury and Balam A Willemsen and H Srikanth and S Sridhar and BK Cho and PC Canfield},
year = {1996},
date = {1996-01-01},
journal = {Physica C: Superconductivity},
volume = {264},
number = {1-2},
pages = {103--108},
publisher = {North-Holland},
abstract = {Measurements of the RF penetration depth λ(T, H, θ) are used to study the superconducting order parameter, vortex dynamics in the mixed state and delineate critical fields in the borocarbide superconductor YNi2B2C. The lower critical field has an anomalous T dependence, Hc1(T) = 1.12[1 − (T/Tc)]kOe, which is, however, consistent with independent superfluid density measurements at microwave frequencies. The vortex response is dominated by viscous flux flow, indicative of extremely weak pinning, and is parameterized by a field scale Hc2, eff. The angular dependence of the vortex contribution λ(θ) is in good agreement with the Coffey-Clem model. Structure is seen in the depairing transition in the vicinity of the upper critical field, with the existence of well-defined critical fields Hc2α, Hc2βand Hc2γ, with the vortex field scale Hc2, eff closest to Hc2β. Overall the measurements indicate that YNi2B2C has a rich and unusual field dependence of its transport parameters.
},
keywords = {Superconductivity},
pubstate = {published},
tppubtype = {article}
}
Measurements of the RF penetration depth λ(T, H, θ) are used to study the superconducting order parameter, vortex dynamics in the mixed state and delineate critical fields in the borocarbide superconductor YNi2B2C. The lower critical field has an anomalous T dependence, Hc1(T) = 1.12[1 − (T/Tc)]kOe, which is, however, consistent with independent superfluid density measurements at microwave frequencies. The vortex response is dominated by viscous flux flow, indicative of extremely weak pinning, and is parameterized by a field scale Hc2, eff. The angular dependence of the vortex contribution λ(θ) is in good agreement with the Coffey-Clem model. Structure is seen in the depairing transition in the vicinity of the upper critical field, with the existence of well-defined critical fields Hc2α, Hc2βand Hc2γ, with the vortex field scale Hc2, eff closest to Hc2β. Overall the measurements indicate that YNi2B2C has a rich and unusual field dependence of its transport parameters.
66.
Buan, J; Stojkovic, Branko P; Israeloff, Nathan; Goldman, AM; Huang, CC; Valls, Oriol T; Jacobs, T; Sridhar, S; Shih, CR; Yang, HD; others,
Experimental investigation of the pairing state of high-temperature superconductors Journal Article
In: Physical Review B, vol. 54, no. 10, pp. 7462, 1996.
Abstract | BibTeX | Tags: Superconductivity
@article{buan1996experimental,
title = {Experimental investigation of the pairing state of high-temperature superconductors},
author = {J Buan and Branko P Stojkovic and Nathan Israeloff and AM Goldman and CC Huang and Oriol T Valls and T Jacobs and S Sridhar and CR Shih and HD Yang and others},
year = {1996},
date = {1996-01-01},
journal = {Physical Review B},
volume = {54},
number = {10},
pages = {7462},
publisher = {APS},
abstract = {To address the issue of the pairing state in high-temperature superconductors, four different experimental investigations have been carried out on a single high-quality, untwinned single crystal of
LuBa
2
Cu
3
O
7
−
δ
. These include measurements of the specific heat in magnetic fields, both near the transition temperature and at low temperatures, investigations of the angular dependence of the transverse magnetic moment in the nonlinear Meissner regime, and the measurement of microwave properties leading to the temperature dependences of the penetration depth and the surface resistance at low temperatures. Some of the results raise questions relating to the existence of a pairing state with line nodes in the energy gap, whereas others appear to be consistent with this picture. The results taken together suggest that studies of the pairing state be examined critically for possible alternative explanations. © 1996 The American Physical Society.
Received 8 April 1996
DOI:https://doi.org/10.1103/PhysRevB.54.7462
©1996 American Physical Society},
keywords = {Superconductivity},
pubstate = {published},
tppubtype = {article}
}
To address the issue of the pairing state in high-temperature superconductors, four different experimental investigations have been carried out on a single high-quality, untwinned single crystal of
LuBa
2
Cu
3
O
7
−
δ
. These include measurements of the specific heat in magnetic fields, both near the transition temperature and at low temperatures, investigations of the angular dependence of the transverse magnetic moment in the nonlinear Meissner regime, and the measurement of microwave properties leading to the temperature dependences of the penetration depth and the surface resistance at low temperatures. Some of the results raise questions relating to the existence of a pairing state with line nodes in the energy gap, whereas others appear to be consistent with this picture. The results taken together suggest that studies of the pairing state be examined critically for possible alternative explanations. © 1996 The American Physical Society.
Received 8 April 1996
DOI:https://doi.org/10.1103/PhysRevB.54.7462
©1996 American Physical Society
LuBa
2
Cu
3
O
7
−
δ
. These include measurements of the specific heat in magnetic fields, both near the transition temperature and at low temperatures, investigations of the angular dependence of the transverse magnetic moment in the nonlinear Meissner regime, and the measurement of microwave properties leading to the temperature dependences of the penetration depth and the surface resistance at low temperatures. Some of the results raise questions relating to the existence of a pairing state with line nodes in the energy gap, whereas others appear to be consistent with this picture. The results taken together suggest that studies of the pairing state be examined critically for possible alternative explanations. © 1996 The American Physical Society.
Received 8 April 1996
DOI:https://doi.org/10.1103/PhysRevB.54.7462
©1996 American Physical Society
65.
Sridhar, S; Oxx, S; Willemsen, Balam A; Srikanth, H; Choudhury, DP
Comment on “Vortex Glass and Lattice Melting Transitions in a YN i 2 B 2 C Single Crystal” Journal Article
In: Physical review letters, vol. 77, no. 10, pp. 2145, 1996.
Abstract | BibTeX | Tags: Superconductivity
@article{sridhar1996comment,
title = {Comment on “Vortex Glass and Lattice Melting Transitions in a YN i 2 B 2 C Single Crystal”},
author = {S Sridhar and S Oxx and Balam A Willemsen and H Srikanth and DP Choudhury},
year = {1996},
date = {1996-01-01},
journal = {Physical review letters},
volume = {77},
number = {10},
pages = {2145},
publisher = {American Physical Society},
abstract = {A Comment on the Letter by Mi-Ock Mun, et al., Phys. Rev. Lett. 76, 2790 (1996). The authors of the Letter offer a Reply.
Received 25 April 1996
DOI:https://doi.org/10.1103/PhysRevLett.77.2145
©1996 American Physical Society},
keywords = {Superconductivity},
pubstate = {published},
tppubtype = {article}
}
A Comment on the Letter by Mi-Ock Mun, et al., Phys. Rev. Lett. 76, 2790 (1996). The authors of the Letter offer a Reply.
Received 25 April 1996
DOI:https://doi.org/10.1103/PhysRevLett.77.2145
©1996 American Physical Society
Received 25 April 1996
DOI:https://doi.org/10.1103/PhysRevLett.77.2145
©1996 American Physical Society
64.
Buan, J; Goldman, Allen M; Huang, Cheng-Cher; Valls, Oriol T; Jacobs, T; Israeloff, Nathan; Sridhar, S; Stojkovic, Branko P; Liu, JZ; Shelton, Robert; others,
The Pairing State of High Temperature Superconductors: Magnetic, Thermal and Microwave Measurements on a Single Crystal Journal Article
In: Turkish Journal of Physics, vol. 20, no. 6, pp. 655–669, 1996.
Abstract | BibTeX | Tags: Superconductivity
@article{buan1996pairing,
title = {The Pairing State of High Temperature Superconductors: Magnetic, Thermal and Microwave Measurements on a Single Crystal},
author = {J Buan and Allen M Goldman and Cheng-Cher Huang and Oriol T Valls and T Jacobs and Nathan Israeloff and S Sridhar and Branko P Stojkovic and JZ Liu and Robert Shelton and others},
year = {1996},
date = {1996-01-01},
journal = {Turkish Journal of Physics},
volume = {20},
number = {6},
pages = {655--669},
publisher = {The Scientific and Technological Research Council of Turkey},
abstract = {The pairing state has been studied through measurements of the transvers magnetic moment in the nonlinear Meissner regime. This investigation, which probes properties over a volume determine by the penetration depth, and is thus a bulk measurement, does not support a pure em{d}-wave picture of the pairing state. The crystal on which much of the data has been obtained was subject to other experimental investigations which reveal it to be of a quality comparable to those of the best cuprate crystals in the YBCO family. These include measurements of the specific heat in magnetic fields, both near the transition temperature and at low temperatures, the measurement of microwave properties leading to the temperature dependences of the penetration depth and the surface resistance at low temperatures. Only the microwave measurements were unequivocally in agreement with the findings of others which have been interpreted as being supportive of emd-wave pairing. This suggests that it is necessary to seek alternative explanations for some data interpreted within a em{d}-wave framework.
Keywords:},
keywords = {Superconductivity},
pubstate = {published},
tppubtype = {article}
}
The pairing state has been studied through measurements of the transvers magnetic moment in the nonlinear Meissner regime. This investigation, which probes properties over a volume determine by the penetration depth, and is thus a bulk measurement, does not support a pure em{d}-wave picture of the pairing state. The crystal on which much of the data has been obtained was subject to other experimental investigations which reveal it to be of a quality comparable to those of the best cuprate crystals in the YBCO family. These include measurements of the specific heat in magnetic fields, both near the transition temperature and at low temperatures, the measurement of microwave properties leading to the temperature dependences of the penetration depth and the surface resistance at low temperatures. Only the microwave measurements were unequivocally in agreement with the findings of others which have been interpreted as being supportive of emd-wave pairing. This suggests that it is necessary to seek alternative explanations for some data interpreted within a em{d}-wave framework.
Keywords:
Keywords:
63.
Jacobs, T; Sridhar, S; Willemsen, BA; Li, Qiang; Gu, GD; Koshizuka, N
Nonlinear microwave switching response of BSCCO single crystals Technical Report
Brookhaven National Lab., Upton, NY (United States) 1996.
Abstract | BibTeX | Tags: Superconductivity
@techreport{jacobs1996nonlinear,
title = {Nonlinear microwave switching response of BSCCO single crystals},
author = {T Jacobs and S Sridhar and BA Willemsen and Qiang Li and GD Gu and N Koshizuka},
year = {1996},
date = {1996-01-01},
institution = {Brookhaven National Lab., Upton, NY (United States)},
abstract = {Measurements of the surface impedance in Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8+{delta}} single crystal with microwave currents flowing along the {cflx c} axis show clear evidence of a step-like nonlinearity. The surface resistance switches between apparently quantized levels for microwave field strength changes < 1 mG. This nonlinear response can arise from the presence of intrinsic Josephson junctions along the {cflx c} axis of these samples driven by the microwave current.},
keywords = {Superconductivity},
pubstate = {published},
tppubtype = {techreport}
}
Measurements of the surface impedance in Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8+{delta}} single crystal with microwave currents flowing along the {cflx c} axis show clear evidence of a step-like nonlinearity. The surface resistance switches between apparently quantized levels for microwave field strength changes < 1 mG. This nonlinear response can arise from the presence of intrinsic Josephson junctions along the {cflx c} axis of these samples driven by the microwave current.
62.
Sridhar, S; Derov, JS; others,
Flux Penetration in patterned high Tc thin films: A study at microwave frequencies Proceedings Article
In: APS March Meeting Abstracts, 1996.
Abstract | BibTeX | Tags: Superconductivity
@inproceedings{sridhar1996flux,
title = {Flux Penetration in patterned high Tc thin films: A study at microwave frequencies},
author = {S Sridhar and JS Derov and others},
year = {1996},
date = {1996-01-01},
booktitle = {APS March Meeting Abstracts},
abstract = {The complex surface impedance Z_S(ω, H_DC, H_RF,T) of patterned YBa_2Cu_3O_7-δ thin films was studied in a number of suspended self-resonant structures, such as rings, meander and straight lines. Several resonances below 20 GHz were studied in fields up to 6 T and for temperatures down to below 4.2 K. ∆ Z_S(H_DC) can be thought of as providing an effective measurement the absolute flux density in the strip. Three distinct regimes of flux penetration are observed: at low fields we observe the initial penetration of flux, a region of non-uniform penetration at moderate fields and ultimately a region where the penetration can be considered as uniform. These three regimes are discussed in terms of recent theoretical results for thin superconducting samples in prependicular fields. The penetration of flux into the sample in regimes 2 and 3 is well described with the field-induced critical state, and the field scale which separates these two regions yields an indirect measure of J_c. The response in decreasing fields cannot simply be describe using the critical state model. Possible origins for this behavior will be discussed. The nonlinear response as a function of microwave power Z_s(H_RF) will also be presented. Supported by Rome Laboratory and the NSF through NSF-DMR-9223850},
keywords = {Superconductivity},
pubstate = {published},
tppubtype = {inproceedings}
}
The complex surface impedance Z_S(ω, H_DC, H_RF,T) of patterned YBa_2Cu_3O_7-δ thin films was studied in a number of suspended self-resonant structures, such as rings, meander and straight lines. Several resonances below 20 GHz were studied in fields up to 6 T and for temperatures down to below 4.2 K. ∆ Z_S(H_DC) can be thought of as providing an effective measurement the absolute flux density in the strip. Three distinct regimes of flux penetration are observed: at low fields we observe the initial penetration of flux, a region of non-uniform penetration at moderate fields and ultimately a region where the penetration can be considered as uniform. These three regimes are discussed in terms of recent theoretical results for thin superconducting samples in prependicular fields. The penetration of flux into the sample in regimes 2 and 3 is well described with the field-induced critical state, and the field scale which separates these two regions yields an indirect measure of J_c. The response in decreasing fields cannot simply be describe using the critical state model. Possible origins for this behavior will be discussed. The nonlinear response as a function of microwave power Z_s(H_RF) will also be presented. Supported by Rome Laboratory and the NSF through NSF-DMR-9223850
61.
Oxx, S; Choudhury, DP; Willemsen, Balam A; Srikanth, H; Sridhar, S; Cho, BK; Canfield, PC
Depairing, Vortex Response and Critical Fields in YNi_2B_2C Proceedings Article
In: APS March Meeting Abstracts, 1996.
Abstract | BibTeX | Tags: Superconductivity
@inproceedings{oxx1996depairing,
title = {Depairing, Vortex Response and Critical Fields in YNi_2B_2C},
author = {S Oxx and DP Choudhury and Balam A Willemsen and H Srikanth and S Sridhar and BK Cho and PC Canfield},
year = {1996},
date = {1996-01-01},
booktitle = {APS March Meeting Abstracts},
abstract = {Measurements of the rf penetration depth lambda (T, H, Theta) are used to study the superconducting order parameter and vortex dynamics in the mixed state in single crystals of the borocarbide superconductor YNi_2B_2C. H_c1= 0.12 (1-t) shows an anomalous variation with T which is consistent with microwave measurements of the superfluid density. In the mixed state for H> H_c1, pinning is very weak and viscous flux flow dominates even at 3 MHz. The flux viscosity (for H< H_c2) is strongly H dependent, consistent with the strong magnetoresistance in the normal state (for H> H_c2). Angular dependence of lambda (T, H, Theta) reveals that H_c2 is isotropic. The H induced depairing transition, observed near H_c2 shows multiple features which is unlike that seen in conventional superconductors. Overall YNi_2B_2C. H_c1 is a superconductor which has anomalous T and H dependences of various parameters …},
keywords = {Superconductivity},
pubstate = {published},
tppubtype = {inproceedings}
}
Measurements of the rf penetration depth lambda (T, H, Theta) are used to study the superconducting order parameter and vortex dynamics in the mixed state in single crystals of the borocarbide superconductor YNi_2B_2C. H_c1= 0.12 (1-t) shows an anomalous variation with T which is consistent with microwave measurements of the superfluid density. In the mixed state for H> H_c1, pinning is very weak and viscous flux flow dominates even at 3 MHz. The flux viscosity (for H< H_c2) is strongly H dependent, consistent with the strong magnetoresistance in the normal state (for H> H_c2). Angular dependence of lambda (T, H, Theta) reveals that H_c2 is isotropic. The H induced depairing transition, observed near H_c2 shows multiple features which is unlike that seen in conventional superconductors. Overall YNi_2B_2C. H_c1 is a superconductor which has anomalous T and H dependences of various parameters …
60.
Srikanth, H; Willemsen, Balam A; Jacobs, T; Sridhar, S; Erb, A; Walker, E; Flukiger, R
New features in the microwave response of YBCO crystals: Evidence for a multi-component order parameter Journal Article
In: arXiv preprint cond-mat/9610032, 1996.
Abstract | BibTeX | Tags: Superconductivity
@article{srikanth1996new,
title = {New features in the microwave response of YBCO crystals: Evidence for a multi-component order parameter},
author = {H Srikanth and Balam A Willemsen and T Jacobs and S Sridhar and A Erb and E Walker and R Flukiger},
year = {1996},
date = {1996-01-01},
journal = {arXiv preprint cond-mat/9610032},
abstract = {New features are reported in precision measurements of the complex microwave conductivity of high quality YBa2Cu3O6.95 crystals grown in BaZrO3 crucibles. A third peak in the normal conductivity, σ1(T), at around 80K, and enhanced pair conductivity σ2(T) below ∼65K are observed. The data are inconsistent with a single order parameter, and instead are indicative of multi-component superconductivity. Overall, these results point to the presence of multiple pairing interactions in YBa2Cu3O6.95 and also provide a natural explanation to account for the low temperature 35K conductivity peak observed in all YBa2Cu3O6.95 crystals.},
keywords = {Superconductivity},
pubstate = {published},
tppubtype = {article}
}
New features are reported in precision measurements of the complex microwave conductivity of high quality YBa2Cu3O6.95 crystals grown in BaZrO3 crucibles. A third peak in the normal conductivity, σ1(T), at around 80K, and enhanced pair conductivity σ2(T) below ∼65K are observed. The data are inconsistent with a single order parameter, and instead are indicative of multi-component superconductivity. Overall, these results point to the presence of multiple pairing interactions in YBa2Cu3O6.95 and also provide a natural explanation to account for the low temperature 35K conductivity peak observed in all YBa2Cu3O6.95 crystals.
59.
Sridhar, S; Oxx, S; Willemsen, Balam A; Srikanth, H; Choudhury, DP
Comment on Journal Article
In: 1996.
Abstract | BibTeX | Tags: Superconductivity
@article{sridhar1996commentb,
title = {Comment on},
author = {S Sridhar and S Oxx and Balam A Willemsen and H Srikanth and DP Choudhury},
year = {1996},
date = {1996-01-01},
abstract = {Comment on “Vortex Glass and Lattice Melting Transitions in a YNi2B2C Single Crystal” In a recent Letter [1], Mun et al. claim to observe vortex glass and lattice melting transitions in superconducting YNi2B2C. A key observation, which they associate with vortex lattice melting, is the presence of a sharp transition in the dc resistivity in finite dc magnetic field. Mun et al. arrive at an HT phase diagram with a single phase boundary which separates the vortex liquid from the vortex solid/glass and a single Hc2 (T) Superconductor-Normal (SN) boundary. In this Comment, we show that precision rf penetration depth measurements indicate a much more complex picture than that presented in Ref.[1].
Our experiments are carried out on samples obtained from the same source as in Ref.[1], using an rf (3 MHz) tunnel diode technique. Details of the measurement technique and particularly results on single crystal YNi2B2C are …},
keywords = {Superconductivity},
pubstate = {published},
tppubtype = {article}
}
Comment on “Vortex Glass and Lattice Melting Transitions in a YNi2B2C Single Crystal” In a recent Letter [1], Mun et al. claim to observe vortex glass and lattice melting transitions in superconducting YNi2B2C. A key observation, which they associate with vortex lattice melting, is the presence of a sharp transition in the dc resistivity in finite dc magnetic field. Mun et al. arrive at an HT phase diagram with a single phase boundary which separates the vortex liquid from the vortex solid/glass and a single Hc2 (T) Superconductor-Normal (SN) boundary. In this Comment, we show that precision rf penetration depth measurements indicate a much more complex picture than that presented in Ref.[1].
Our experiments are carried out on samples obtained from the same source as in Ref.[1], using an rf (3 MHz) tunnel diode technique. Details of the measurement technique and particularly results on single crystal YNi2B2C are …
Our experiments are carried out on samples obtained from the same source as in Ref.[1], using an rf (3 MHz) tunnel diode technique. Details of the measurement technique and particularly results on single crystal YNi2B2C are …
58.
Sridhar, S; Oxx, S; Willemsen, BA; Srikanth, H; Choudhury, DP
Vortex glass and lattice melting transitions in a YNi2B2C single crystal-Comment Journal Article
In: PHYSICAL REVIEW LETTERS, vol. 77, no. 10, pp. 2145–2145, 1996.
BibTeX | Tags: Superconductivity
@article{sridhar1996vortex,
title = {Vortex glass and lattice melting transitions in a YNi2B2C single crystal-Comment},
author = {S Sridhar and S Oxx and BA Willemsen and H Srikanth and DP Choudhury},
year = {1996},
date = {1996-01-01},
journal = {PHYSICAL REVIEW LETTERS},
volume = {77},
number = {10},
pages = {2145--2145},
publisher = {AMERICAN PHYSICAL SOC ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA},
keywords = {Superconductivity},
pubstate = {published},
tppubtype = {article}
}
57.
Srikanth, H; Zhai, Z; Sridhar, S; Gajewski, DA; Maple, MB
Microwave surface impedance of Pr_xY_1-xBa_2Cu_3O_7-delta single crystals Proceedings Article
In: APS March Meeting Abstracts, 1996.
Abstract | BibTeX | Tags: Superconductivity
@inproceedings{srikanth1996microwave,
title = {Microwave surface impedance of Pr_xY_1-xBa_2Cu_3O_7-delta single crystals},
author = {H Srikanth and Z Zhai and S Sridhar and DA Gajewski and MB Maple},
year = {1996},
date = {1996-01-01},
booktitle = {APS March Meeting Abstracts},
abstract = {Measurements of the complex surface impedance Z_s (T)= R_s+ imu_0omegalambda have been carried out on Pr_xY_1-xBa_2Cu_3O_7-delta single crystals in a high-Q superconducting Nb cavity resonating at 10 GHz. Sample T_c's range from 92 K to 15 K as the Pr content (x) is increased from 0.0 to 0.8. A systematic analysis of the extracted surface resistance R_s (T) and penetration depth lambda (T) for increasing Pr concentration will be presented. The low temperature variation of lambda (T) shows a gradual crossover from a linear dependence (for x= 0.0) to a power-law behavior for higher Pr doping. The effect of enhanced scattering associated with random Pr substitution at the Y sites is reflected in the observed changes in the temperature dependence of Z_s. Novel structure in the transition region is observed which is not seen in dc resistivity or magnetic susceptibility. Magnetic scattering introduced by the …},
keywords = {Superconductivity},
pubstate = {published},
tppubtype = {inproceedings}
}
Measurements of the complex surface impedance Z_s (T)= R_s+ imu_0omegalambda have been carried out on Pr_xY_1-xBa_2Cu_3O_7-delta single crystals in a high-Q superconducting Nb cavity resonating at 10 GHz. Sample T_c's range from 92 K to 15 K as the Pr content (x) is increased from 0.0 to 0.8. A systematic analysis of the extracted surface resistance R_s (T) and penetration depth lambda (T) for increasing Pr concentration will be presented. The low temperature variation of lambda (T) shows a gradual crossover from a linear dependence (for x= 0.0) to a power-law behavior for higher Pr doping. The effect of enhanced scattering associated with random Pr substitution at the Y sites is reflected in the observed changes in the temperature dependence of Z_s. Novel structure in the transition region is observed which is not seen in dc resistivity or magnetic susceptibility. Magnetic scattering introduced by the …
56.
Sridhar, S; Jacobs, T; Willemsen, Balam A; Srikanth, H
Penetration depth and non-linear microwave driven Josephson response of BSCCO crystals. Proceedings Article
In: APS March Meeting Abstracts, 1996.
Abstract | BibTeX | Tags: Superconductivity
@inproceedings{sridhar1996penetration,
title = {Penetration depth and non-linear microwave driven Josephson response of BSCCO crystals.},
author = {S Sridhar and T Jacobs and Balam A Willemsen and H Srikanth},
year = {1996},
date = {1996-01-01},
booktitle = {APS March Meeting Abstracts},
abstract = {Precision measurements of the in-plane (lambda_ab) and the widehatc-axis (lambda_c) microwave penetration depth of BSCCO crystals are reported (T. Jacobs, S. Sridhar, Q. Li, GD Gu, N. Koshizuka, Phys. Rev. Lett.(to appear).). At low T, lambda_ab has a leading linear T dependence, similar to YBCO crystals, and consistent with nodes in the in-plane superconducting gap. These results resolve earlier controversies, and suggest that BSCCO and YBCO have similar energy dependence of the quasiparticle density of states. lambda_c (T) is also consistent with models of direct tunneling across superconducting layers with nodes in the gap. A novel non-linear microwave response is also observed which we associate with microwave critical currents through Josephson junctions along the widehatc-axis. This non-linearity results in``quantized''microwave surface resistance (R_s) steps, with the crystal apparently …},
keywords = {Superconductivity},
pubstate = {published},
tppubtype = {inproceedings}
}
Precision measurements of the in-plane (lambda_ab) and the widehatc-axis (lambda_c) microwave penetration depth of BSCCO crystals are reported (T. Jacobs, S. Sridhar, Q. Li, GD Gu, N. Koshizuka, Phys. Rev. Lett.(to appear).). At low T, lambda_ab has a leading linear T dependence, similar to YBCO crystals, and consistent with nodes in the in-plane superconducting gap. These results resolve earlier controversies, and suggest that BSCCO and YBCO have similar energy dependence of the quasiparticle density of states. lambda_c (T) is also consistent with models of direct tunneling across superconducting layers with nodes in the gap. A novel non-linear microwave response is also observed which we associate with microwave critical currents through Josephson junctions along the widehatc-axis. This non-linearity results in``quantized''microwave surface resistance (R_s) steps, with the crystal apparently …
1995
55.
Jacobs, T; Sridhar, S; Li, Qiang; Gu, GD; Koshizuka, N
In-Plane and c^-Axis Microwave Penetration Depth of Bi 2 Sr 2 Ca 1 Cu 2 O 8+ $delta$ Crystals Journal Article
In: Physical review letters, vol. 75, no. 24, pp. 4516, 1995.
BibTeX | Tags: Superconductivity
@article{jacobs1995plane,
title = {In-Plane and c^-Axis Microwave Penetration Depth of Bi 2 Sr 2 Ca 1 Cu 2 O 8+ $delta$ Crystals},
author = {T Jacobs and S Sridhar and Qiang Li and GD Gu and N Koshizuka},
year = {1995},
date = {1995-01-01},
journal = {Physical review letters},
volume = {75},
number = {24},
pages = {4516},
publisher = {APS},
keywords = {Superconductivity},
pubstate = {published},
tppubtype = {article}
}
54.
Jacobs, T; Willemsen, Balam A; Sridhar, S; Nagarajan, R; Gupta, LC; Hossain, Z; Mazumdar, Chandan; Canfield, PC; Cho, BK
Microwave properties of borocarbide superconductors R Ni 2 B 2 C (R= Y, Er, Tm, Ho) Journal Article
In: Physical Review B, vol. 52, no. 10, pp. R7022, 1995.
Abstract | BibTeX | Tags: Superconductivity
@article{jacobs1995microwave,
title = {Microwave properties of borocarbide superconductors R Ni 2 B 2 C (R= Y, Er, Tm, Ho)},
author = {T Jacobs and Balam A Willemsen and S Sridhar and R Nagarajan and LC Gupta and Z Hossain and Chandan Mazumdar and PC Canfield and BK Cho},
year = {1995},
date = {1995-01-01},
journal = {Physical Review B},
volume = {52},
number = {10},
pages = {R7022},
publisher = {APS},
abstract = {We report measurements of the microwave surface impedance of the borocarbide family of superconductors R Ni 2 B 2 C (R= Y, Er, Tm, Ho). The experiments enable direct measurements of the superfluid density, and are particularly sensitive to the influence of magnetic pair breaking. In HoNi 2 B 2 C the antiferromagnetic transition is clearly observed at zero field, and leads to a drastic reduction of the superfluid density, which recovers at lower temperatures. In ErNi 2 B 2 C the antiferromagnetic transition is not seen in zero-field data. Magnetic effects are responsible for anomalies in the low-temperature surface impedance below approximately 4 K in HoNi 2 B 2 C and TmNi 2 B 2 C. The temperature dependence of the microwave impedance disagrees with BCS calculations.},
keywords = {Superconductivity},
pubstate = {published},
tppubtype = {article}
}
We report measurements of the microwave surface impedance of the borocarbide family of superconductors R Ni 2 B 2 C (R= Y, Er, Tm, Ho). The experiments enable direct measurements of the superfluid density, and are particularly sensitive to the influence of magnetic pair breaking. In HoNi 2 B 2 C the antiferromagnetic transition is clearly observed at zero field, and leads to a drastic reduction of the superfluid density, which recovers at lower temperatures. In ErNi 2 B 2 C the antiferromagnetic transition is not seen in zero-field data. Magnetic effects are responsible for anomalies in the low-temperature surface impedance below approximately 4 K in HoNi 2 B 2 C and TmNi 2 B 2 C. The temperature dependence of the microwave impedance disagrees with BCS calculations.
53.
Jacobs, T; Sridhar, S; Rieck, CT; Scharnberg, K; Wolf, T; Halbritter, J
Microwave Surface Impedance of YBCO: 123 crystals: Experiment and comparison to a d-wave model Journal Article
In: 1995.
Abstract | BibTeX | Tags: Superconductivity
@article{jacobs1995microwaveb,
title = {Microwave Surface Impedance of YBCO: 123 crystals: Experiment and comparison to a d-wave model},
author = {T Jacobs and S Sridhar and CT Rieck and K Scharnberg and T Wolf and J Halbritter},
year = {1995},
date = {1995-01-01},
abstract = {We present measurements of the microwave surface resistance Rs and the penetration depth lambda of YBCO: 123 crystals. At low T obeys lambda (T) a polynomial behavior, while Rs displays a characteristic non-monotonic T-dependence.
A detailed comparison of the experimental data is made to a model of d-wave superconductivity which includes both elastic and inelastic scattering. While the model reproduces the general features of the experimental data, three aspects of the parameters needed are worth noting. The elastic scattering rate required to fit the data is much smaller than measured from the normal state, the scattering phase shifts have to be close to pi/2 and a strong coupling value of the gap parameter 2Delta (0)/kTc= 6 is needed. On the experimental side the uncertainties regarding the material parameters lambda (0) and Rs, res (0) further complicate a quantitative comparison.},
keywords = {Superconductivity},
pubstate = {published},
tppubtype = {article}
}
We present measurements of the microwave surface resistance Rs and the penetration depth lambda of YBCO: 123 crystals. At low T obeys lambda (T) a polynomial behavior, while Rs displays a characteristic non-monotonic T-dependence.
A detailed comparison of the experimental data is made to a model of d-wave superconductivity which includes both elastic and inelastic scattering. While the model reproduces the general features of the experimental data, three aspects of the parameters needed are worth noting. The elastic scattering rate required to fit the data is much smaller than measured from the normal state, the scattering phase shifts have to be close to pi/2 and a strong coupling value of the gap parameter 2Delta (0)/kTc= 6 is needed. On the experimental side the uncertainties regarding the material parameters lambda (0) and Rs, res (0) further complicate a quantitative comparison.
A detailed comparison of the experimental data is made to a model of d-wave superconductivity which includes both elastic and inelastic scattering. While the model reproduces the general features of the experimental data, three aspects of the parameters needed are worth noting. The elastic scattering rate required to fit the data is much smaller than measured from the normal state, the scattering phase shifts have to be close to pi/2 and a strong coupling value of the gap parameter 2Delta (0)/kTc= 6 is needed. On the experimental side the uncertainties regarding the material parameters lambda (0) and Rs, res (0) further complicate a quantitative comparison.
52.
Willemsen, Balam A; Derov, John S; Silva, José H; Sridhar, S
Nonlinear response of suspended high temperature superconducting thin film microwave resonators Journal Article
In: IEEE Transactions on Applied Superconductivity, vol. 5, no. 2, pp. 1753–1755, 1995.
Abstract | BibTeX | Tags: Superconductivity
@article{willemsen1995nonlinear,
title = {Nonlinear response of suspended high temperature superconducting thin film microwave resonators},
author = {Balam A Willemsen and John S Derov and José H Silva and S Sridhar},
year = {1995},
date = {1995-01-01},
journal = {IEEE Transactions on Applied Superconductivity},
volume = {5},
number = {2},
pages = {1753--1755},
publisher = {IEEE},
abstract = {The nonlinear microwave surface impedance, Z/sub s/(H/sub rf/) of Y/sub 1/Ba/sub 2/Cu/sub 3/O/sub 7/(-/spl delta/) thin films is measured using suspended patterned resonators. We find that the nonlinear response is well described in terms of a single mechanism, namely the hysteretic ac response of the current-induced critical state.< >},
keywords = {Superconductivity},
pubstate = {published},
tppubtype = {article}
}
The nonlinear microwave surface impedance, Z/sub s/(H/sub rf/) of Y/sub 1/Ba/sub 2/Cu/sub 3/O/sub 7/(-/spl delta/) thin films is measured using suspended patterned resonators. We find that the nonlinear response is well described in terms of a single mechanism, namely the hysteretic ac response of the current-induced critical state.< >
51.
Willemsen, Balam A; Sridhar, S; Derov, John S; Silva, José H
Vortex dynamics at microwave frequencies in patterned YBa2Cu3O7- $delta$ thin films Journal Article
In: Applied physics letters, vol. 67, no. 4, pp. 551–553, 1995.
BibTeX | Tags: Superconductivity
@article{willemsen1995vortex,
title = {Vortex dynamics at microwave frequencies in patterned YBa2Cu3O7- $delta$ thin films},
author = {Balam A Willemsen and S Sridhar and John S Derov and José H Silva},
year = {1995},
date = {1995-01-01},
journal = {Applied physics letters},
volume = {67},
number = {4},
pages = {551--553},
publisher = {American Institute of Physics},
keywords = {Superconductivity},
pubstate = {published},
tppubtype = {article}
}
50.
JACOBS, T; SRIDHAR, S; RIECK, CT; SCHARNBERG, K; WOLF, T; HALBRITTER, I
MICROWAVE SURFACE IMPEDANCE OF YiBa2Cu307-5 CRYSTALS: EXPERIMENT AND COMPARISON TO A</-WAVE MODEL Journal Article
In: JOURNAL OF PHYSICS ANB CHEMISTRY OF SOLIDS, pp. 1945, 1995.
Abstract | BibTeX | Tags: Superconductivity
@article{jacobs1995microwavec,
title = {MICROWAVE SURFACE IMPEDANCE OF YiBa2Cu307-5 CRYSTALS: EXPERIMENT AND COMPARISON TO A</-WAVE MODEL},
author = {T JACOBS and S SRIDHAR and CT RIECK and K SCHARNBERG and T WOLF and I HALBRITTER},
year = {1995},
date = {1995-01-01},
journal = {JOURNAL OF PHYSICS ANB CHEMISTRY OF SOLIDS},
pages = {1945},
abstract = {We present measurements of the microwave surface resistance Rs and the penetration depth A of YiBa2Cu307-ä crystals. At low T, MT) obeys a polynomial behavior, while Rs displays a characteristic non-monotonic T-dependence. A detailed comparison of the experimental data is made to a model of d-wave superconductivity which includes both elastic and inelastic scattering. While the model reproduces the general features of the experimental data, three aspects of the parameters needed are worth noting. The elastic scattering rate required to fit the data is much smaller than measured from the normal state, the scattering phase shifts have to be close to TT/2 and a strong coupling value of the gap parameter 2A (0)/krc~ 6 is needed. On the experimental side the uncertainties regarding the material parameters A (0) and As, res (0) further complicate a quantitative comparison. For one sample, i? s, res (0) agrees with the intrinsic value which results from the rf-wave model.},
keywords = {Superconductivity},
pubstate = {published},
tppubtype = {article}
}
We present measurements of the microwave surface resistance Rs and the penetration depth A of YiBa2Cu307-ä crystals. At low T, MT) obeys a polynomial behavior, while Rs displays a characteristic non-monotonic T-dependence. A detailed comparison of the experimental data is made to a model of d-wave superconductivity which includes both elastic and inelastic scattering. While the model reproduces the general features of the experimental data, three aspects of the parameters needed are worth noting. The elastic scattering rate required to fit the data is much smaller than measured from the normal state, the scattering phase shifts have to be close to TT/2 and a strong coupling value of the gap parameter 2A (0)/krc~ 6 is needed. On the experimental side the uncertainties regarding the material parameters A (0) and As, res (0) further complicate a quantitative comparison. For one sample, i? s, res (0) agrees with the intrinsic value which results from the rf-wave model.
49.
Jacobs, T; Sridhar, S; Rieck, CT; Scharnberg, K; Wolf, T; Halbritter, J
Microwave surface impedance of Y1Ba2Cu3O7- $delta$ crystals: Experiment and comparison to a d-wave model Journal Article
In: Journal of Physics and Chemistry of Solids, vol. 56, no. 12, pp. 1945–1949, 1995.
BibTeX | Tags: Superconductivity
@article{jacobs1995microwaved,
title = {Microwave surface impedance of Y1Ba2Cu3O7- $delta$ crystals: Experiment and comparison to a d-wave model},
author = {T Jacobs and S Sridhar and CT Rieck and K Scharnberg and T Wolf and J Halbritter},
year = {1995},
date = {1995-01-01},
journal = {Journal of Physics and Chemistry of Solids},
volume = {56},
number = {12},
pages = {1945--1949},
publisher = {Pergamon},
keywords = {Superconductivity},
pubstate = {published},
tppubtype = {article}
}
48.
Jacobs, T; Sridhar, S; Li, Q; Gu, GD; Koshizuka, N
In-plane and $$cflx $$ital c$$$$-axis microwave penetration depth of Bi $$sub 2$$ Sr $$sub 2$$ Ca $$sub 1$$ Cu $$sub 2$$ O $$sub 8+$$delta$$$$ crystals Journal Article
In: Physical Review Letters, vol. 75, no. 24, 1995.
BibTeX | Tags: Superconductivity
@article{jacobs1995planeb,
title = {In-plane and $$cflx $$ital c$$$$-axis microwave penetration depth of Bi $$sub 2$$ Sr $$sub 2$$ Ca $$sub 1$$ Cu $$sub 2$$ O $$sub 8+$$delta$$$$ crystals},
author = {T Jacobs and S Sridhar and Q Li and GD Gu and N Koshizuka},
year = {1995},
date = {1995-01-01},
journal = {Physical Review Letters},
volume = {75},
number = {24},
publisher = {Brookhaven National Lab.(BNL), Upton, NY (United States)},
keywords = {Superconductivity},
pubstate = {published},
tppubtype = {article}
}
47.
Jacobs, T; Willemsen, BA; Sridhar, S; Nagarajan, R; Gupta, LC; Hossain, Z; Mazumdar, C; Canfield, PC; Cho, BK
Microwave properties of borocarbide superconductors $$ital R$$ Ni $$sub 2$$ B $$sub 2$$ C ($$ital R$$= Y, Er, Tm, Ho) Journal Article
In: Physical Review, B: Condensed Matter, vol. 52, no. 10, 1995.
BibTeX | Tags: Superconductivity
@article{jacobs1995microwavee,
title = {Microwave properties of borocarbide superconductors $$ital R$$ Ni $$sub 2$$ B $$sub 2$$ C ($$ital R$$= Y, Er, Tm, Ho)},
author = {T Jacobs and BA Willemsen and S Sridhar and R Nagarajan and LC Gupta and Z Hossain and C Mazumdar and PC Canfield and BK Cho},
year = {1995},
date = {1995-01-01},
journal = {Physical Review, B: Condensed Matter},
volume = {52},
number = {10},
publisher = {Ames National Laboratory},
keywords = {Superconductivity},
pubstate = {published},
tppubtype = {article}
}
1994
46.
Sridhar, S
Nonlinear microwave impedance of superconductors and ac response of the critical state Journal Article
In: Applied physics letters, vol. 65, no. 8, pp. 1054–1056, 1994.
Abstract | BibTeX | Tags: Superconductivity
@article{sridhar1994nonlinear,
title = {Nonlinear microwave impedance of superconductors and ac response of the critical state},
author = {S Sridhar},
year = {1994},
date = {1994-01-01},
journal = {Applied physics letters},
volume = {65},
number = {8},
pages = {1054--1056},
publisher = {American Institute of Physics},
abstract = {The hysteretic ac response of the current‐induced critical state of superconducting wires (strips of circular or rectangular cross‐section) is expressed in a surface impedance formulation. The results for the rectangular strip are shown to be in good agreement with experimental results on the high power nonlinear response of superconducting microwave devices. The approach provides a proper framework to understand such nonlinear response.},
keywords = {Superconductivity},
pubstate = {published},
tppubtype = {article}
}
The hysteretic ac response of the current‐induced critical state of superconducting wires (strips of circular or rectangular cross‐section) is expressed in a surface impedance formulation. The results for the rectangular strip are shown to be in good agreement with experimental results on the high power nonlinear response of superconducting microwave devices. The approach provides a proper framework to understand such nonlinear response.
45.
Chen, HJ; Owliaei, J; Sridhar, S
Modulated microwave surface impedance of superconducting films Journal Article
In: Review of scientific instruments, vol. 65, no. 8, pp. 2635–2640, 1994.
Abstract | BibTeX | Tags: Superconductivity
@article{chen1994modulated,
title = {Modulated microwave surface impedance of superconducting films},
author = {HJ Chen and J Owliaei and S Sridhar},
year = {1994},
date = {1994-01-01},
journal = {Review of scientific instruments},
volume = {65},
number = {8},
pages = {2635--2640},
publisher = {American Institute of Physics},
abstract = {We present details of an experimental method to measure the field modulated surface resistance (dRs/dH) of superconducting films accurately, which enables both field and temperature sweep experiments and is particularly useful for low‐field or near Tc measurements. The complex surface impedance Zs(H,T)=Rs(H,T)+iXs(H,T) can also be simultaneously measured. This technique utilizes specially built circuitry to lock the microwave source to the cavity and keep the input power of the cavity constant, even as the resonant frequency or Q value of the cavity changes with changing temperature or applied field. With the above circuitry, we were able to measure (dRs/dH) directly rather than (dP/dH) as in some modulated microwave absorption measurements. With the high accuracy offered by the modulation technique and the high Q of the cavity, important information about the magnetic‐field response of superconducting films, such as dynamics of vortices and low‐field properties of weak links can be obtained. The technique can also be employed to measure any possible spontaneously induced internal fields in two‐dimensional high‐Tc superconductors.},
keywords = {Superconductivity},
pubstate = {published},
tppubtype = {article}
}
We present details of an experimental method to measure the field modulated surface resistance (dRs/dH) of superconducting films accurately, which enables both field and temperature sweep experiments and is particularly useful for low‐field or near Tc measurements. The complex surface impedance Zs(H,T)=Rs(H,T)+iXs(H,T) can also be simultaneously measured. This technique utilizes specially built circuitry to lock the microwave source to the cavity and keep the input power of the cavity constant, even as the resonant frequency or Q value of the cavity changes with changing temperature or applied field. With the above circuitry, we were able to measure (dRs/dH) directly rather than (dP/dH) as in some modulated microwave absorption measurements. With the high accuracy offered by the modulation technique and the high Q of the cavity, important information about the magnetic‐field response of superconducting films, such as dynamics of vortices and low‐field properties of weak links can be obtained. The technique can also be employed to measure any possible spontaneously induced internal fields in two‐dimensional high‐Tc superconductors.
44.
Oxx, S; Willemsen, Balam A; Li, Qiang; Shibutani, K; Shigaki, I; Ogawa, R; Sridhar, S
Penetration depth and microwave surface resistance of Bi2Sr2CaCu2O8 single crystals Journal Article
In: Physica C: Superconductivity, vol. 235, pp. 889–890, 1994.
Abstract | BibTeX | Tags: Superconductivity
@article{oxx1994penetration,
title = {Penetration depth and microwave surface resistance of Bi2Sr2CaCu2O8 single crystals},
author = {S Oxx and Balam A Willemsen and Qiang Li and K Shibutani and I Shigaki and R Ogawa and S Sridhar},
year = {1994},
date = {1994-01-01},
journal = {Physica C: Superconductivity},
volume = {235},
pages = {889--890},
publisher = {North-Holland},
abstract = {The penetration depth λ and the surface resistance Rs of BSCCO single crystals were measured at 10 GHz using a special Nb cavity. At low temperatures, δλ ∞ T2, inconsistent with pure s- or d- wave symmetry, but suggestive of strong impurity scattering. Near Tc the data are inconsistent with a two-fluid of BCS s-wave model. An unusual peak is observed in Rs near Tc and is attributed to fluctuations.},
keywords = {Superconductivity},
pubstate = {published},
tppubtype = {article}
}
The penetration depth λ and the surface resistance Rs of BSCCO single crystals were measured at 10 GHz using a special Nb cavity. At low temperatures, δλ ∞ T2, inconsistent with pure s- or d- wave symmetry, but suggestive of strong impurity scattering. Near Tc the data are inconsistent with a two-fluid of BCS s-wave model. An unusual peak is observed in Rs near Tc and is attributed to fluctuations.
1992
43.
Owliaei, J; Sridhar, S; Talvacchio, J
Field-dependent crossover in the vortex response at microwave frequencies in YBa 2 Cu 3 O 7- $delta$ films Journal Article
In: Physical review letters, vol. 69, no. 23, pp. 3366, 1992.
BibTeX | Tags: Superconductivity
@article{owliaei1992field,
title = {Field-dependent crossover in the vortex response at microwave frequencies in YBa 2 Cu 3 O 7- $delta$ films},
author = {J Owliaei and S Sridhar and J Talvacchio},
year = {1992},
date = {1992-01-01},
journal = {Physical review letters},
volume = {69},
number = {23},
pages = {3366},
publisher = {American Physical Society},
keywords = {Superconductivity},
pubstate = {published},
tppubtype = {article}
}
42.
Sridhar, S; Maheswaran, B; Willemsen, Balam A; Wu, Dong Ho; Haddon, RC
Scaling behavior of the rf vortex penetration depth in an organic superconductor Journal Article
In: Physical review letters, vol. 68, no. 14, pp. 2220, 1992.
Abstract | BibTeX | Tags: Superconductivity
@article{sridhar1992scaling,
title = {Scaling behavior of the rf vortex penetration depth in an organic superconductor},
author = {S Sridhar and B Maheswaran and Balam A Willemsen and Dong Ho Wu and RC Haddon},
year = {1992},
date = {1992-01-01},
journal = {Physical review letters},
volume = {68},
number = {14},
pages = {2220},
publisher = {APS},
abstract = {The radiofrequency penetration depth λ (H, T) of the organic superconductor (BEDT-TTF) 2 Cu (NCS) 2 was studied in the mixed state at moderate fields. The data can be scaled into a single functional form Δλ (H, T)= Δ λ*(T) f (H/H*(T)), where H*(T)×(1-t) 3/2/t can be identified with a ‘‘depinning’’or ‘‘irreversibility’’line. We show that the scaling features are contained in a theory of vortex motion in a periodic pootential under the influence of thermal fluctuations, which describes the functional form quantitatively. The data for Δλ (H= 0, T) are governed by the same (vortex) length scale as the finite-field data, suggesting that the zero-field state is not a conventional Meissner state obeying a London relation.},
keywords = {Superconductivity},
pubstate = {published},
tppubtype = {article}
}
The radiofrequency penetration depth λ (H, T) of the organic superconductor (BEDT-TTF) 2 Cu (NCS) 2 was studied in the mixed state at moderate fields. The data can be scaled into a single functional form Δλ (H, T)= Δ λ*(T) f (H/H*(T)), where H*(T)×(1-t) 3/2/t can be identified with a ‘‘depinning’’or ‘‘irreversibility’’line. We show that the scaling features are contained in a theory of vortex motion in a periodic pootential under the influence of thermal fluctuations, which describes the functional form quantitatively. The data for Δλ (H= 0, T) are governed by the same (vortex) length scale as the finite-field data, suggesting that the zero-field state is not a conventional Meissner state obeying a London relation.
41.
Rath, S; Sridhar, S
Core instability of elliptic drift vortices Journal Article
In: Physics of Fluids B: Plasma Physics, vol. 4, no. 5, pp. 1367–1369, 1992.
Abstract | BibTeX | Tags: Superconductivity
@article{rath1992core,
title = {Core instability of elliptic drift vortices},
author = {S Rath and S Sridhar},
year = {1992},
date = {1992-01-01},
journal = {Physics of Fluids B: Plasma Physics},
volume = {4},
number = {5},
pages = {1367--1369},
publisher = {American Institute of Physics},
abstract = {It is shown that two‐dimensional drift vortices with elliptic cores are unstable to certain short‐wavelength three‐dimensional perturbations. Circular vortices are stable to those modes. At short wavelengths, the growth rate is independent of the wavelength and, for small ellipticity, it is proportional to the ellipticity.},
keywords = {Superconductivity},
pubstate = {published},
tppubtype = {article}
}
It is shown that two‐dimensional drift vortices with elliptic cores are unstable to certain short‐wavelength three‐dimensional perturbations. Circular vortices are stable to those modes. At short wavelengths, the growth rate is independent of the wavelength and, for small ellipticity, it is proportional to the ellipticity.
40.
Sridhar, S
EM Properties of High Tc Superconductors Technical Report
DTIC Document 1992.
Abstract | BibTeX | Tags: Superconductivity
@techreport{sridhar1992properties,
title = {EM Properties of High Tc Superconductors},
author = {S Sridhar},
year = {1992},
date = {1992-01-01},
institution = {DTIC Document},
abstract = {The aim of this contract was to study the factors influencing microwave properties9 of high1 TrV smiperconductuirs, via fundamental measurements on high quality thin film and s;ingle- cryqta1 material,~. Two principal lines of investigation were pursued: Tn single crystals of Y1BaCuOQ>5 (Tc=93K) ultrasensitive rf methods were used to study the penetration depth X, lower critical fields Hc1 and vortex pinning forces. The i penetration depth and surf. ace resistance were found to obey temperature dependencesi good agreemont with BCS calculations. The anisotropy and temperature dependence of
Itwere measured and also found to tie in good agreement with 13CS theory. The
pinning forrc'o were measured, and the results imply that In good quality single
crystals, tht. pinning is due to core pinning by defects, and implies intrinsic
critical currents 2x10'A/cM2.},
keywords = {Superconductivity},
pubstate = {published},
tppubtype = {techreport}
}
The aim of this contract was to study the factors influencing microwave properties9 of high1 TrV smiperconductuirs, via fundamental measurements on high quality thin film and s;ingle- cryqta1 material,~. Two principal lines of investigation were pursued: Tn single crystals of Y1BaCuOQ>5 (Tc=93K) ultrasensitive rf methods were used to study the penetration depth X, lower critical fields Hc1 and vortex pinning forces. The i penetration depth and surf. ace resistance were found to obey temperature dependencesi good agreemont with BCS calculations. The anisotropy and temperature dependence of
Itwere measured and also found to tie in good agreement with 13CS theory. The
pinning forrc'o were measured, and the results imply that In good quality single
crystals, tht. pinning is due to core pinning by defects, and implies intrinsic
critical currents 2x10'A/cM2.
Itwere measured and also found to tie in good agreement with 13CS theory. The
pinning forrc'o were measured, and the results imply that In good quality single
crystals, tht. pinning is due to core pinning by defects, and implies intrinsic
critical currents 2x10'A/cM2.
1991
39.
Wei, Y-Z; Sridhar, S
Radiation-corrected open-ended coax line technique for dielectric measurements of liquids up to 20 GHz Journal Article
In: IEEE Transactions on Microwave Theory and Techniques, vol. 39, no. 3, pp. 526–531, 1991.
Abstract | BibTeX | Tags: Superconductivity
@article{wei1991radiation,
title = {Radiation-corrected open-ended coax line technique for dielectric measurements of liquids up to 20 GHz},
author = {Y-Z Wei and S Sridhar},
year = {1991},
date = {1991-01-01},
journal = {IEEE Transactions on Microwave Theory and Techniques},
volume = {39},
number = {3},
pages = {526--531},
publisher = {IEEE},
abstract = {An experimental technique and associated analysis are described for the measurement of the dielectric constants of liquids at microwave frequencies using an open-ended coax probe. The analysis includes radiative corrections to the probe-liquid interface impedance. The technique is applicable to liquid and liquid-like (e.g., biological) samples, having dielectric constants comparable to water, at frequencies up to 20 GHz and possibly as high as 40 GHz.<>},
keywords = {Superconductivity},
pubstate = {published},
tppubtype = {article}
}
An experimental technique and associated analysis are described for the measurement of the dielectric constants of liquids at microwave frequencies using an open-ended coax probe. The analysis includes radiative corrections to the probe-liquid interface impedance. The technique is applicable to liquid and liquid-like (e.g., biological) samples, having dielectric constants comparable to water, at frequencies up to 20 GHz and possibly as high as 40 GHz.<>
38.
Zahopoulos, C; Sridhar, S; Bautista, JJ; Ortiz, G; Lanagan, M
Performance of a high T c superconducting ultralow-loss microwave stripline filter Journal Article
In: Applied physics letters, vol. 58, no. 9, pp. 977–979, 1991.
BibTeX | Tags: Superconductivity
@article{zahopoulos1991performance,
title = {Performance of a high T c superconducting ultralow-loss microwave stripline filter},
author = {C Zahopoulos and S Sridhar and JJ Bautista and G Ortiz and M Lanagan},
year = {1991},
date = {1991-01-01},
journal = {Applied physics letters},
volume = {58},
number = {9},
pages = {977--979},
publisher = {American Institute of Physics},
keywords = {Superconductivity},
pubstate = {published},
tppubtype = {article}
}
37.
Wu, Dong-Ho; Sridhar, S
Erratum:``Pinning forces and lowere critical fields in YBa2Cu3Oy crystals: Temperature dependence and anisotropy''[Phys. Rev. Lett. 65, 2074 (1990)] Journal Article
In: Physical Review Letters, vol. 66, pp. 968–968, 1991.
BibTeX | Tags: Superconductivity
@article{wu1991erratum,
title = {Erratum:``Pinning forces and lowere critical fields in YBa2Cu3Oy crystals: Temperature dependence and anisotropy''[Phys. Rev. Lett. 65, 2074 (1990)]},
author = {Dong-Ho Wu and S Sridhar},
year = {1991},
date = {1991-01-01},
journal = {Physical Review Letters},
volume = {66},
pages = {968--968},
keywords = {Superconductivity},
pubstate = {published},
tppubtype = {article}
}
36.
Bautista, JJ; Ortiz, GERARDOG; Zahopoulos, C; Sridhar, S; Lanagan, M
Performance of a high T (sub c) superconducting ultra-low loss microwave stripline filter Journal Article
In: 1991.
Abstract | BibTeX | Tags: Superconductivity
@article{bautista1991performance,
title = {Performance of a high T (sub c) superconducting ultra-low loss microwave stripline filter},
author = {JJ Bautista and GERARDOG Ortiz and C Zahopoulos and S Sridhar and M Lanagan},
year = {1991},
date = {1991-01-01},
abstract = {Discussed here is the successful fabrication of a five-pole interdigital stripline filter made of the 93 K superconductor (Y1Ba2Cu3O sub y) coated on a silver substrate, with center frequency of 8.5 GHz and an extremely high rejection ratio of 80 dB. The lowest injection loss measured was 0.1 dB at 12 K, with a return loss of better than 16 dB, representing a significant improvement over a similar copper filter, and is comparable to low critical temperature filters. The insertion loss appears to be limited by extrinsic factors, such as tuning mismatch and joint losses, and not by superconducting material losses.},
keywords = {Superconductivity},
pubstate = {published},
tppubtype = {article}
}
Discussed here is the successful fabrication of a five-pole interdigital stripline filter made of the 93 K superconductor (Y1Ba2Cu3O sub y) coated on a silver substrate, with center frequency of 8.5 GHz and an extremely high rejection ratio of 80 dB. The lowest injection loss measured was 0.1 dB at 12 K, with a return loss of better than 16 dB, representing a significant improvement over a similar copper filter, and is comparable to low critical temperature filters. The insertion loss appears to be limited by extrinsic factors, such as tuning mismatch and joint losses, and not by superconducting material losses.
35.
Wu, Dong-Ho; Sridhar, S
Wu and Sridhar reply Journal Article
In: Physical review letters, vol. 67, no. 11, pp. 1474, 1991.
Abstract | BibTeX | Tags: Superconductivity
@article{wu1991wu,
title = {Wu and Sridhar reply},
author = {Dong-Ho Wu and S Sridhar},
year = {1991},
date = {1991-01-01},
journal = {Physical review letters},
volume = {67},
number = {11},
pages = {1474},
publisher = {APS},
abstract = {A reply to the comment on relation between Bc and pinning-force constant in YBaCuO is given. The authors claim they did not say Bc is anisotropic, and though Bc is isotropic, pinning-force constant need not be. The relation between these two arises under assumptions of core pinning.(AIP)},
keywords = {Superconductivity},
pubstate = {published},
tppubtype = {article}
}
A reply to the comment on relation between Bc and pinning-force constant in YBaCuO is given. The authors claim they did not say Bc is anisotropic, and though Bc is isotropic, pinning-force constant need not be. The relation between these two arises under assumptions of core pinning.(AIP)
1990
34.
Wu, Dong-Ho; Sridhar, S
Pinning forces and lower critical fields in YBa 2 Cu 3 O y crystals: Temperature dependence and anisotropy Journal Article
In: Physical review letters, vol. 65, no. 16, pp. 2074, 1990.
Abstract | BibTeX | Tags: Superconductivity
@article{wu1990pinning,
title = {Pinning forces and lower critical fields in YBa 2 Cu 3 O y crystals: Temperature dependence and anisotropy},
author = {Dong-Ho Wu and S Sridhar},
year = {1990},
date = {1990-01-01},
journal = {Physical review letters},
volume = {65},
number = {16},
pages = {2074},
publisher = {APS},
abstract = {Measurements of the field-dependent radiofrequency penetration depth λ (H, T) are used to delineate the lower-critical-field H c 1-T phase boundary, and to study flux dynamics in YBa 2 Cu 3 O y crystals. For both H∥ c^ and H⊥ c^ H c 1 obeys a BCS temperature dependence with a temperature-independent anisotropy of 3.4±0.3. In the mixed state, the data obey λ 2 (H)=[φ 0/μ 0 α (T)] B (H), and yield both the functional dependence B (H) and the pinning force constant α (T). The latter is anisotropic, obeys an approximately (1-t 2) 2 temperature dependence, and vanishes slightly below the bulk transition temperature.},
keywords = {Superconductivity},
pubstate = {published},
tppubtype = {article}
}
Measurements of the field-dependent radiofrequency penetration depth λ (H, T) are used to delineate the lower-critical-field H c 1-T phase boundary, and to study flux dynamics in YBa 2 Cu 3 O y crystals. For both H∥ c^ and H⊥ c^ H c 1 obeys a BCS temperature dependence with a temperature-independent anisotropy of 3.4±0.3. In the mixed state, the data obey λ 2 (H)=[φ 0/μ 0 α (T)] B (H), and yield both the functional dependence B (H) and the pinning force constant α (T). The latter is anisotropic, obeys an approximately (1-t 2) 2 temperature dependence, and vanishes slightly below the bulk transition temperature.
33.
Sridhar, S
Electrodynamics of Superconducting Y 1 Ba 2 Cu 3 O y Book Section
In: Superconductivity and Applications, pp. 207–215, Springer, Boston, MA, 1990.
BibTeX | Tags: Superconductivity
@incollection{sridhar1990electrodynamics,
title = {Electrodynamics of Superconducting Y 1 Ba 2 Cu 3 O y},
author = {S Sridhar},
year = {1990},
date = {1990-01-01},
booktitle = {Superconductivity and Applications},
pages = {207--215},
publisher = {Springer, Boston, MA},
keywords = {Superconductivity},
pubstate = {published},
tppubtype = {incollection}
}
1989
32.
Sridhar, S
ELECTRODYNAMICS OF SUPERCONDUCTING YjBajCuaO Journal Article
In: Superconductivity and Applications, pp. 207, 1989.
Abstract | BibTeX | Tags: Superconductivity
@article{sridhar1989electrodynamics,
title = {ELECTRODYNAMICS OF SUPERCONDUCTING YjBajCuaO},
author = {S Sridhar},
year = {1989},
date = {1989-01-01},
journal = {Superconductivity and Applications},
pages = {207},
publisher = {Plenum Publishing Corporation},
abstract = {The response of superconductors to time-varying electromagnetic fields can yield detailed information on the nature of the superconducting state1. Experiments carried out at frequencies in the rf to mm-wave spectral region directly probe the collective response of the condensed electrons and of the quasiparticles, and in conventional superconductors, have been important in determining the gap, the density of states and confirming the nature of the pairing.
The basic parameter that is measured at these frequencies is the complex surface impedance Zs= R «+ i Xs. The surface resistance Rt is a measure of the power absorbed, while the surface reactance, which is proportional to the penetration depth A, is a measure of the reactive power exchanged between the field and the superconductors. These quantities can be computed, from the fundamental constitutive relation which relates current and vector potential for the supercoaductor, J=-QA, along with Maxwell's equation and suitable boundary conditions. Experiments can then be compared with detailed predictions for the kernel Q from microscopic theories.},
keywords = {Superconductivity},
pubstate = {published},
tppubtype = {article}
}
The response of superconductors to time-varying electromagnetic fields can yield detailed information on the nature of the superconducting state1. Experiments carried out at frequencies in the rf to mm-wave spectral region directly probe the collective response of the condensed electrons and of the quasiparticles, and in conventional superconductors, have been important in determining the gap, the density of states and confirming the nature of the pairing.
The basic parameter that is measured at these frequencies is the complex surface impedance Zs= R «+ i Xs. The surface resistance Rt is a measure of the power absorbed, while the surface reactance, which is proportional to the penetration depth A, is a measure of the reactive power exchanged between the field and the superconductors. These quantities can be computed, from the fundamental constitutive relation which relates current and vector potential for the supercoaductor, J=-QA, along with Maxwell's equation and suitable boundary conditions. Experiments can then be compared with detailed predictions for the kernel Q from microscopic theories.
The basic parameter that is measured at these frequencies is the complex surface impedance Zs= R «+ i Xs. The surface resistance Rt is a measure of the power absorbed, while the surface reactance, which is proportional to the penetration depth A, is a measure of the reactive power exchanged between the field and the superconductors. These quantities can be computed, from the fundamental constitutive relation which relates current and vector potential for the supercoaductor, J=-QA, along with Maxwell's equation and suitable boundary conditions. Experiments can then be compared with detailed predictions for the kernel Q from microscopic theories.
31.
Sridhar, S; Wu, Dong-Ho; Kennedy, W
Temperature dependence of electrodynamic properties of YBa 2 Cu 3 O y crystals Journal Article
In: Physical review letters, vol. 63, no. 17, pp. 1873, 1989.
Abstract | BibTeX | Tags: Superconductivity
@article{sridhar1989temperature,
title = {Temperature dependence of electrodynamic properties of YBa 2 Cu 3 O y crystals},
author = {S Sridhar and Dong-Ho Wu and W Kennedy},
year = {1989},
date = {1989-01-01},
journal = {Physical review letters},
volume = {63},
number = {17},
pages = {1873},
publisher = {APS},
abstract = {The temperature dependences of the radio-frequency penetration depth λ ab, microwave surface resistance R s, and the lower critical field H c 1 were measured for YBa 2 Cu 3 O y crystals. Pair-breaking effects of magnetic fields on λ ab, represented by a parameter k== d λ ab/d (H 2), were also measured. The temperature dependences of all these parameters λ ab, H c 1, k, and R s are in good agreement with the Bardeen-Cooper-Schrieffer temperature dependences for an s-wave superconductor, and suggest a mean-field behavior of the gap parameter.},
keywords = {Superconductivity},
pubstate = {published},
tppubtype = {article}
}
The temperature dependences of the radio-frequency penetration depth λ ab, microwave surface resistance R s, and the lower critical field H c 1 were measured for YBa 2 Cu 3 O y crystals. Pair-breaking effects of magnetic fields on λ ab, represented by a parameter k== d λ ab/d (H 2), were also measured. The temperature dependences of all these parameters λ ab, H c 1, k, and R s are in good agreement with the Bardeen-Cooper-Schrieffer temperature dependences for an s-wave superconductor, and suggest a mean-field behavior of the gap parameter.
30.
Wu, Dong-Ho; Kennedy, WL; Zahopoulos, C; Sridhar, S
Characteristics and growth of single crystals of Y1Ba2Cu3O7 with superior microwave properties Journal Article
In: Applied physics letters, vol. 55, no. 7, pp. 696–698, 1989.
Abstract | BibTeX | Tags: Superconductivity
@article{wu1989characteristics,
title = {Characteristics and growth of single crystals of Y1Ba2Cu3O7 with superior microwave properties},
author = {Dong-Ho Wu and WL Kennedy and C Zahopoulos and S Sridhar},
year = {1989},
date = {1989-01-01},
journal = {Applied physics letters},
volume = {55},
number = {7},
pages = {696--698},
publisher = {American Institute of Physics},
abstract = {We report the fabrication and high‐frequency characterization of single crystals of Y1Ba2Cu3O7 with extremely sharp microwave transitions. The 10 GHz surface resistance Rs is less than 400 μΩ, at temperatures 4 K below the transition temperature. The electrodynamic characteristics of these crystals were examined via several measurements, and we demonstrate that high quality crystals which show very low Rs also possess small penetration depths λ(0)=1600 Å and small magnetic field effects on the penetration depth characterized by k(0)≡(dλ/dB2)T→0=10−3 Å/G2. In polycrystals, and even in poor single crystals, the presence of Josephson junctions of typical effective area ∼4 μm2 leads to poor microwave properties, with electrodynamic parameters orders of magnitude larger.},
keywords = {Superconductivity},
pubstate = {published},
tppubtype = {article}
}
We report the fabrication and high‐frequency characterization of single crystals of Y1Ba2Cu3O7 with extremely sharp microwave transitions. The 10 GHz surface resistance Rs is less than 400 μΩ, at temperatures 4 K below the transition temperature. The electrodynamic characteristics of these crystals were examined via several measurements, and we demonstrate that high quality crystals which show very low Rs also possess small penetration depths λ(0)=1600 Å and small magnetic field effects on the penetration depth characterized by k(0)≡(dλ/dB2)T→0=10−3 Å/G2. In polycrystals, and even in poor single crystals, the presence of Josephson junctions of typical effective area ∼4 μm2 leads to poor microwave properties, with electrodynamic parameters orders of magnitude larger.
29.
Sridhar, S
Electrodynamics of superconducting Y sub 1 Ba sub 2 Cu sub 3 O sub y Journal Article
In: Superconductivity and Applications, pp. 207–15, 1989.
Abstract | BibTeX | Tags: Superconductivity
@article{sridhar1989electrodynamicsb,
title = {Electrodynamics of superconducting Y sub 1 Ba sub 2 Cu sub 3 O sub y},
author = {S Sridhar},
year = {1989},
date = {1989-01-01},
journal = {Superconductivity and Applications},
pages = {207--15},
abstract = {Discussion includes measurements of surface resistance and penetration depth carried out at rf and microwave frequencies on title crystals. (meeting proceedings).},
keywords = {Superconductivity},
pubstate = {published},
tppubtype = {article}
}
Discussion includes measurements of surface resistance and penetration depth carried out at rf and microwave frequencies on title crystals. (meeting proceedings).
