@article{sridhar2023trueb,

title = {True superconductivity at near ambient temperature has not been confirmed by Dasenbrock-Gammon et al. Nature, volume 615, pages 244–250 (2023)},

author = {Srinivas Sridhar},

year  = {2023},

date = {2023-01-01},

urldate = {2023-01-01},

journal = {Journal of Physics and Chemistry of Solids},

pages = {111381},

publisher = {Pergamon},

keywords = {Superconductivity},

pubstate = {published},

tppubtype = {article}

}

@article{choudhury2008harmonic,

title = {Harmonic generation from YBa2Cu3O7- $delta$ microwave resonators},

author = {Durga P Choudhury and John S Derov and S Sridhar},

year  = {2008},

date = {2008-01-01},

journal = {Measurement},

keywords = {Superconductivity},

pubstate = {published},

tppubtype = {article}

}

@article{choudhury2005superconducting,

title = {Superconducting microwave technology},

author = {Durga P Choudhury and S Sridhar},

year  = {2005},

date = {2005-01-01},

journal = {Encyclopedia of RF and Microwave Engineering},

publisher = {John Wiley & Sons, Inc. Hoboken, NJ, USA},

abstract = {Superconductivity is a remarkable state of matter in which electric current can flow inside materials without any detectable resistance. In a superconductor, perfect electric conductivity or zero resistivity occurs only below a “critical temperature” TC. A direct current induced in a superconducting ring has been shown to persist for over 2 years without any measurable decay. Another important characteristic of superconductors was the discovery by W. Meissner and R. Ochsenfeld in 1933 that a superconductor expels all magnetic flux from its interior; that is, a superconductor is also a perfect diamagnet. A key area of technological applications of superconductors is in high‐frequency devices, particularly at frequencies in the radiowave, microwave, and millimeterwave spectral ranges.},

keywords = {Superconductivity},

pubstate = {published},

tppubtype = {article}

}

@article{kusko2002anomalous,

title = {Anomalous microwave conductivity due to collective transport in the pseudogap state of cuprate superconductors},

author = {C Kusko and Z Zhai and N Hakim and RS Markiewicz and S Sridhar and D Colson and V Viallet-Guillen and A Forget and Yu A Nefyodov and MR Trunin and others},

year  = {2002},

date = {2002-01-01},

journal = {Physical Review B},

volume = {65},

number = {13},

pages = {132501},

publisher = {APS},

abstract = {The microwave surface impedance Z s= R s+ i X s of HgBa 2 Ca 2 Cu 3 O 8+ δ, HgBa 2 CuO 4+ δ, Tl 2 Ba 2 CuO 6+ δ, and underdoped YBa 2 Cu 3 O 6.5 is found to be anomalous in that R s (T> T c)≠ X s (T> T c) in the pseudogap state. This implies plasmonlike response and negative permittivities ɛ′(ω)< 0 at microwave frequencies indicating non-Fermi-liquid transport in the ab plane. The anomalous microwave response is shown to arise from a collective mode characterized by a plasma frequency ω pCM∼ 0.1 eV and extremely low damping Γ CM∼ 10− 5–10− 4 eV, distinctly different from those observed at optical frequencies.},

keywords = {Superconductivity},

pubstate = {published},

tppubtype = {article}

}

@article{hakim2002superconducting,

title = {The superconducting gap of in situ MgB 2 thin films by microwave surface impedance measurements},

author = {N Hakim and C Kusko and S Sridhar and A Soukiassian and XH Zeng and XX Xi},

year  = {2002},

date = {2002-01-01},

journal = {Applied Physics Letters},

volume = {81},

number = {19},

pages = {3603--3605},

publisher = {American Institute of Physics},

keywords = {Superconductivity},

pubstate = {published},

tppubtype = {article}

}

@article{kusko2001anomalousb,

title = {Anomalous scattering rate and microwave absorption in Bi₂Sr₂CaCu₂O₈₊ $delta$ and Y Ba₂Cu₃O₇₋ $delta$},

author = {C Kusko and Z Zhai and RS Markiewicz and S Sridhar},

year  = {2001},

date = {2001-01-01},

keywords = {Superconductivity},

pubstate = {published},

tppubtype = {article}

}

@article{hakim2001microwave,

title = {Microwave properties of superconducting MgB 2},

author = {N Hakim and PV Parimi and C Kusko and S Sridhar and Paul C Canfield and Sergey L Bud’ko and Douglas K Finnemore},

year  = {2001},

date = {2001-01-01},

journal = {Applied Physics Letters},

volume = {78},

number = {26},

pages = {4160--4162},

publisher = {American Institute of Physics},

keywords = {Superconductivity},

pubstate = {published},

tppubtype = {article}

}

@article{zhai2001onset,

title = {Onset of dielectric modes at 110 K and 60 K due to local lattice distortions in nonsuperconducting YBa 2 Cu 3 O 6.0 crystals},

author = {Z Zhai and PV Parimi and JB Sokoloff and S Sridhar and A Erb},

year  = {2001},

date = {2001-01-01},

journal = {Physical Review B},

volume = {63},

number = {9},

pages = {092508},

publisher = {APS},

abstract = {We report the observation of two dielectric transitions at 110 and 60 K in the microwave response of nonsuperconducting YBa 2 Cu 3 O 6.0 crystals. The transitions are characterized by a change in polarizability and presence of loss peaks, associated with overdamped dielectric modes. An explanation is presented in terms of changes in polarizability of the apical O atoms in the Ba–O layer, affected by lattice softening at 110 K, due to change in buckling of the Cu–O layer. The onset of another mode at 60 K strongly suggests an additional local lattice change at this temperature. Thus microwave dielectric measurements are sensitive indicators of lattice softening which may be relevant to superconductivity.},

keywords = {Superconductivity},

pubstate = {published},

tppubtype = {article}

}

@article{dasgupta2001computer,

title = {Computer-aided modeling of superconducting striplines with ground planes using critical state models},

author = {T Dasgupta and JS Derov and S Sridhar},

year  = {2001},

date = {2001-01-01},

journal = {Journal of Applied Physics},

volume = {90},

number = {6},

pages = {2915--2918},

publisher = {American Institute of Physics},

abstract = {The effect of ground planes on the current-induced critical states and flux penetration for a thin superconducting strip carrying a microwave current has been calculated numerically. The nonlinear response represented by the dependence of the surface resistance and reactance were also calculated. We find that when the distance d between the ground planes is smaller than the width a of the strip, i.e., d⩽a, the ground planes affect the nonlinear response significantly. In particular we study the effects of ground planes placed at a distance d=a/5. We compare and contrast these effects with the results of similar models without the ground planes. The ground planes reduce the current crowding at the film edges, thus reducing the nonlinearities arising from critical state flux motion. The numerical procedure can be incorporated into computer-aided design of superconducting microwave circuits.},

keywords = {Superconductivity},

pubstate = {published},

tppubtype = {article}

}

@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 = {Superconductivity},

pubstate = {published},

tppubtype = {article}

}

@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 = {Superconductivity},

pubstate = {published},

tppubtype = {article}

}

@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 = {Superconductivity},

pubstate = {published},

tppubtype = {article}

}

@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 = {Superconductivity},

pubstate = {published},

tppubtype = {article}

}

@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 = {Superconductivity},

pubstate = {published},

tppubtype = {article}

}

@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 = {Superconductivity},

pubstate = {published},

tppubtype = {article}

}

@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 = {Superconductivity},

pubstate = {published},

tppubtype = {article}

}

@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 = {Superconductivity},

pubstate = {published},

tppubtype = {article}

}

@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 = {Superconductivity},

pubstate = {published},

tppubtype = {article}

}

@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 = {Magnetism, Superconductivity},

pubstate = {published},

tppubtype = {article}

}

@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 = {Superconductivity},

pubstate = {published},

tppubtype = {article}

}

@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 = {Magnetism, Superconductivity},

pubstate = {published},

tppubtype = {article}

}

@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 = {Superconductivity},

pubstate = {published},

tppubtype = {article}

}

@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 = {Superconductivity},

pubstate = {published},

tppubtype = {article}

}

@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 = {Superconductivity},

pubstate = {published},

tppubtype = {article}

}

@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 = {Superconductivity},

pubstate = {published},

tppubtype = {article}

}

@article{srikanth1998systematics,

title = {Systematics of two-component superconductivity in YBa 2 Cu 3 O 6.95 from microwave measurements of high-quality single crystals},

author = {H Srikanth and Z Zhai and S Sridhar and A Erb and E Walker},

year  = {1998},

date = {1998-01-01},

journal = {Physical Review B},

volume = {57},

number = {13},

pages = {7986},

publisher = {APS},

abstract = {A systematic set of measurements of the microwave (10 GHz) surface impedance 

(

Z

s

=

R

s

+

i

X

s

)

 of twinned 

YBa

2

Cu

3

O

6.95

 single crystals (called YBCO/BZO) grown in 

BaZrO

3

 crucibles reveal properties that are not directly seen in similar measurements on other YBCO samples. The complex conductivity 

σ

=

σ

1

−

i

σ

2

 obtained as a function of temperature 

(

T

)

 from the surface impedance data shows two key features: (1) A conductivity peak in 

σ

1

(

T

)

 around 

80

 K in addition to peaks at 

30

 K and 

92

 K and (2) extra pairing below 

65

 K in addition to the onset of pairing below the bulk 

T

c

 of 

93.4

 K as revealed in 

σ

2

(

T

)

. These features are present in all three YBCO/BZO crystals measured and are absent in YBCO crystals grown by other methods. These results show that in addition to pairing at 

T

c

=

 

93.4

 K, an additional pairing channel opens up at 

(

∼

65

 K). High-pressure oxygenation of one of the crystals still yields the same results, and shows that the data cannot be due to unwanted macroscopic segregation of O-deficient regions. Systematics on three single crystals show that the height of the quasiparticle conductivity peak at 

80

 K in the superconducting state is correlated with the inelastic scattering rate in the normal state. Close to 

T

c

,

 

σ

2

(

T

)

∼

(

T

c

−

T

)

, indicating a mean-field behavior and inconsistent with 

3

D

X

Y

 fluctuations over a wide temperature range. A single complex order parameter cannot describe these data, and the results suggest that at least two superconducting components with corresponding pairing temperature scales 

(

T

A

∼65 K and 

T

B

=

T

c

=93.4 K) are required. Comparison to model calculations considering various decoupled two-component scenarios 

(

A

+

B

=

d

+

s

,

s

+

d

,

d

+

d

)

 are presented. The comparison shows that the experimental data do not distinguish between these various scenarios, however, the data do require that one of the components be an order parameter with nodes in the gap, such as a 

d

-wave order parameter. Fit parameters to the calculations using the different scenarios are presented. These components are naturally present in all YBCO samples, however, impurities appear to suppress the pair density of the low-temperature 

A

 component and lead to greatly enhanced scattering of the high-temperature 

B

 component. Overall, our results strongly suggest the presence of multiple pairing temperature scales and energies in 

YBa

2

Cu

3

O

6

.

95

.},

keywords = {Superconductivity},

pubstate = {published},

tppubtype = {article}

}

@article{srikanth1998microwave,

title = {Microwave properties of YBCO crystals grown in BaZrO3 crucibles: influence of c-axis currents},

author = {H Srikanth and Z Zhai and S Sridhar and A Erb},

year  = {1998},

date = {1998-01-01},

journal = {Journal of Physics and Chemistry of Solids},

volume = {59},

number = {10-12},

pages = {2105--2109},

publisher = {Pergamon},

abstract = {Measurements of the ab-plane complex microwave conductivity of high quality YBa2Cu3O6.95 single crystals indicate the presence of a pairing temperature scale around 65 K in addition to the bulk Tc of 93.4 K. Qualitatively similar behavior is seen for the case when microwave current flow in both ab-plane and along the c-axis. Influence of c-axis currents tends to broaden the feature in the superfluid density around 65 K. The extracted c-axis low temperature penetration depth, λc(T), shows a linear dependence with a slope nearly 10 times larger than that of λab(T).},

keywords = {Superconductivity},

pubstate = {published},

tppubtype = {article}

}

@article{choudhury1998magnetoelectrodynamics,

title = {Magnetoelectrodynamics at high frequencies in the antiferromagnetic and superconducting states of DyNi 2 B 2 C},

author = {Durga P Choudhury and H Srikanth and S Sridhar and PC Canfield},

year  = {1998},

date = {1998-01-01},

journal = {Physical Review B},

volume = {58},

number = {21},

pages = {14490},

publisher = {APS},

abstract = {We report our observation of the behavior of the radio frequency (rf) and microwave response of 

DyNi

2

B

2

C

 over a wide range of temperature (T) and magnetic field (H) in the antiferromagnetic (AFM) and superconducting (SC) states. At microwave frequencies of 10 GHz, the T dependence of the surface impedance 

Z

s

=

R

s

+

i

X

s

 was measured which yields the T dependence of the complex conductivity 

σ

1

−

i

σ

2

 in the SC and AFM states. At radio frequencies (4 MHz), the H and T dependence of the penetration depth 

λ

(

T

,

H

)

 were measured. The establishment of antiferromagnetic order at 

T

N

=

10.3

K

 results in a marked decrease in the scattering of charge carriers, leading to sharp decreases in 

R

s

 and 

X

s

.

 However, 

R

s

 and 

X

s

 differ from each other in the AFM state. We show that the results are consistent with relaxation processes whence the scattering rate becomes comparable to the microwave frequency. The rf measurements yield a rich dependence of the scattering on the magnetic field near and below 

T

N

.

 Anomalous decrease of scattering at moderate applied fields is observed at temperatures near and above 

T

N

,

 and arises due to a crossover from a negative magnetoresistance state, possibly associated with a loss of spin disorder scattering at low fields, to a positive magnetoresistance state associated with the metallic nature. The normal state magnetoresistance is positive at all temperatures for 

μ

0

H

>

2

T

 and at all fields for 

T

>

15

K

.

 Several characteristic field scales associated with metamagnetic transitions 

[

H

M

1

(

T

)

,

H

M

2

(

T

)

]

,

 the onset of spin disorder 

H

D

(

T

)

 and the upper critical field 

H

c

2

(

T

)

 are observed in the rf measurements.},

keywords = {Superconductivity},

pubstate = {published},

tppubtype = {article}

}

@article{srikanth9610032new,

title = {New Features in the Microwave Response of YBa 2 Cu 3 O 6.95 Crystals: Evidence for a Multicomponent Order Parameter},

author = {H Srikanth and BA Willemson and T Jacobs and S Sridhar},

year  = {1997},

date = {1997-06-01},

journal = {arXiv preprint cond-mat/9610032},

abstract = {New features are reported in precision measurements of the complex microwave conductivity of high-quality YBa 2 Cu 3 O 6.95 crystals grown in BaZrO 3 crucibles. A third peak in the normal conductivity, σ 1 (T), at around 80 K, and enhanced pair conductivity σ 2 (T) below∼ 65 K are observed. The data are inconsistent with a single order parameter, and instead are indicative of multicomponent superconductivity. Overall, these results point to the presence of multiple pairing interactions in YBa 2 Cu 3 O 6.95 and also provide a natural explanation to account for the low-temperature 35-K conductivity peak observed in all YBa 2 Cu 3 O 6.95 crystals.},

keywords = {Superconductivity},

pubstate = {published},

tppubtype = {article}

}

@article{eskildsen1997observation,

title = {Observation of a field-driven structural phase transition in the flux line lattice in ErNi 2 B 2 C},

author = {MR Eskildsen and PL Gammel and BP Barber and U Yaron and AP Ramirez and DA Huse and DJ Bishop and C Bolle and CM Lieber and S Oxx and others},

year  = {1997},

date = {1997-01-01},

journal = {Physical review letters},

volume = {78},

number = {10},

pages = {1968},

publisher = {American Physical Society},

keywords = {Superconductivity},

pubstate = {published},

tppubtype = {article}

}

@article{srikanth1997microwave,

title = {Microwave response of YBa 2 Cu 3 O 6.95 crystals: Evidence for a multicomponent order parameter},

author = {H Srikanth and Balam A Willemsen and T Jacobs and S Sridhar and A Erb and E Walker and R Flükiger},

year  = {1997},

date = {1997-01-01},

journal = {Physical Review B},

volume = {55},

number = {22},

pages = {R14733},

publisher = {APS},

abstract = {New features are reported in precision measurements of the complex microwave conductivity of high-quality YBa 2 Cu 3 O 6.95 crystals grown in BaZrO 3 crucibles. A third peak in the normal conductivity, σ 1 (T), at around 80 K, and enhanced pair conductivity σ 2 (T) below∼ 65 K are observed. The data are inconsistent with a single order parameter, and instead are indicative of multicomponent superconductivity. Overall, these results point to the presence of multiple pairing interactions in YBa 2 Cu 3 O 6.95 and also provide a natural explanation to account for the low-temperature 35-K conductivity peak observed in all YBa 2 Cu 3 O 6.95 crystals.},

keywords = {Superconductivity},

pubstate = {published},

tppubtype = {article}

}