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41.
Srikanth, H; Revcolevschi, B; Choudhury, DP; Sridhar, S; Pinsard, L; Revcolevschi, A
High frequency electrodynamics of La_1-xSr_xMnO3 single crystals Proceedings Article
In: APS March Meeting Abstracts, 1998.
@inproceedings{srikanth1998highb,
title = {High frequency electrodynamics of La_1-xSr_xMnO3 single crystals},
author = {H Srikanth and B Revcolevschi and DP Choudhury and S Sridhar and L Pinsard and A Revcolevschi},
year = {1998},
date = {1998-01-01},
booktitle = {APS March Meeting Abstracts},
abstract = {The electrodynamic response of La_1-xSr_xMnO 3 single crsytals at radio-frequencies (RF) reveal a variety of features associated with the structural, magnetic and electronic properties of the system. Insulating and metallic samples with varying Sr content were investigated using a very sensitive RF inductance technique operating at 3 MHz. A colossal frequency shift is observed at the ferromagnetic (FM) transition and sharp changes are seen at the orthorhombic structural transitions associated with Jahn-Teller distortions. In addition, our experiments show rich structure in the different phases which are not clearly observed in conventional DC magnetization and transport experiments. A phase diagram with the characteristic temperature and field scales derived from our high frequency measurements is obtained. Microwave surface impedance results at 10 GHz on the metallic samples will also be presented. Overall …},
keywords = {},
pubstate = {published},
tppubtype = {inproceedings}
}
The electrodynamic response of La_1-xSr_xMnO 3 single crsytals at radio-frequencies (RF) reveal a variety of features associated with the structural, magnetic and electronic properties of the system. Insulating and metallic samples with varying Sr content were investigated using a very sensitive RF inductance technique operating at 3 MHz. A colossal frequency shift is observed at the ferromagnetic (FM) transition and sharp changes are seen at the orthorhombic structural transitions associated with Jahn-Teller distortions. In addition, our experiments show rich structure in the different phases which are not clearly observed in conventional DC magnetization and transport experiments. A phase diagram with the characteristic temperature and field scales derived from our high frequency measurements is obtained. Microwave surface impedance results at 10 GHz on the metallic samples will also be presented. Overall …
42.
Srikanth, H; Zhai, Z; Sridhar, S; Erb, A; Walker, E
Systematics of two-component superconductivity in YBa 2 Cu 3 O 6.95 from microwave measurements of high-quality single crystals Journal Article
In: Physical Review B, vol. 57, no. 13, pp. 7986, 1998.
@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 = {},
pubstate = {published},
tppubtype = {article}
}
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
.
(
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
.
43.
Zhai, Z; Srikanth, H; Sridhar, S; Erb, A
Microwave properties of YBCO and other cuprate single crystals Proceedings Article
In: APS March Meeting Abstracts, 1998.
@inproceedings{zhai1998microwave,
title = {Microwave properties of YBCO and other cuprate single crystals},
author = {Z Zhai and H Srikanth and S Sridhar and A Erb},
year = {1998},
date = {1998-01-01},
booktitle = {APS March Meeting Abstracts},
abstract = {We report on a systematic study of the surface impedance (Z_s= R_s+ i X_s) of YBCO single crystals grown in BaZrO 3 crucibles. The experiments were done using a superconducting cavity resonator made of Nb operating at 10 GHz. The complex conductivity sigma= sigma 1-i sigma 2 reveal new features which are associated with onset of extra pairing below 65 K in addition to pairing below the bulk T c of 93.4 K. Our data suggests that a single complex order parameter cannot describe these data and at least two superconducting components are required. Comparison to model calculations using various two-component scenarios will be presented which effectively demonstrate this behavior. Analysis reveal that it is essential to have one of the components to have an underlying d-wave symmetry to describe the data. Overall, our results strongly suggest the presence of multiple pairing temperature scales in YBCO …},
keywords = {},
pubstate = {published},
tppubtype = {inproceedings}
}
We report on a systematic study of the surface impedance (Z_s= R_s+ i X_s) of YBCO single crystals grown in BaZrO 3 crucibles. The experiments were done using a superconducting cavity resonator made of Nb operating at 10 GHz. The complex conductivity sigma= sigma 1-i sigma 2 reveal new features which are associated with onset of extra pairing below 65 K in addition to pairing below the bulk T c of 93.4 K. Our data suggests that a single complex order parameter cannot describe these data and at least two superconducting components are required. Comparison to model calculations using various two-component scenarios will be presented which effectively demonstrate this behavior. Analysis reveal that it is essential to have one of the components to have an underlying d-wave symmetry to describe the data. Overall, our results strongly suggest the presence of multiple pairing temperature scales in YBCO …
44.
Bansil, A; Markiewicz, B; Sridhar, S; Liebenberg, D
Spectroscopies in novel superconductors-Preface Miscellaneous
1998.
@misc{bansil1998spectroscopies,
title = {Spectroscopies in novel superconductors-Preface},
author = {A Bansil and B Markiewicz and S Sridhar and D Liebenberg},
year = {1998},
date = {1998-01-01},
publisher = {PERGAMON-ELSEVIER SCIENCE LTD THE BOULEVARD, LANGFORD LANE, KIDLINGTON~…},
keywords = {},
pubstate = {published},
tppubtype = {misc}
}
45.
Srikanth, H; Zhai, Z; Sridhar, S; Erb, A
Microwave properties of YBCO crystals grown in BaZrO3 crucibles: influence of c-axis currents Journal Article
In: Journal of Physics and Chemistry of Solids, vol. 59, no. 10-12, pp. 2105–2109, 1998.
@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 = {},
pubstate = {published},
tppubtype = {article}
}
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).
46.
Choudhury, Durga P; Srikanth, H; Sridhar, S; Canfield, PC
Magnetoelectrodynamics at high frequencies in the antiferromagnetic and superconducting states of DyNi 2 B 2 C Journal Article
In: Physical Review B, vol. 58, no. 21, pp. 14490, 1998.
@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 = {},
pubstate = {published},
tppubtype = {article}
}
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.
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.
47.
Choudhury, Durga P; Derov, John S; Sridhar, S
Measurement and modeling of nonlinear microwave response of high temperature superconductors Proceedings Article
In: APS March Meeting Abstracts, 1998.
@inproceedings{choudhury1998measurement,
title = {Measurement and modeling of nonlinear microwave response of high temperature superconductors},
author = {Durga P Choudhury and John S Derov and S Sridhar},
year = {1998},
date = {1998-01-01},
booktitle = {APS March Meeting Abstracts},
abstract = {Results of experiments carried out to probe the nonlinear microwave response of epitaxial thin film YBa_2Cu_3O_7-delta resonators under a variety of conditions, including the application of a very small DC magnetic field is described. The suspended geometry used in the setup has no superconducting ground planes and is thus highly sensitive to low applied fields which was parallel to the c-axis of the film. Measurement of harmonic power generation and intermodulation products as a function of temperature and applied field show several novel features in the region of parameter space where< A HREF= http://sagar. physics. neu. edu/preprints. html> earlier measurements of surface resistance(R_S) have shown a marked decrease in nonlinearity and R_S. The observed results will be discussed in the context of the Critical State and other models of vortex dynamics in HTSC materials. A finite element numerical …},
keywords = {},
pubstate = {published},
tppubtype = {inproceedings}
}
Results of experiments carried out to probe the nonlinear microwave response of epitaxial thin film YBa_2Cu_3O_7-delta resonators under a variety of conditions, including the application of a very small DC magnetic field is described. The suspended geometry used in the setup has no superconducting ground planes and is thus highly sensitive to low applied fields which was parallel to the c-axis of the film. Measurement of harmonic power generation and intermodulation products as a function of temperature and applied field show several novel features in the region of parameter space where< A HREF= http://sagar. physics. neu. edu/preprints. html> earlier measurements of surface resistance(R_S) have shown a marked decrease in nonlinearity and R_S. The observed results will be discussed in the context of the Critical State and other models of vortex dynamics in HTSC materials. A finite element numerical …
48.
Srikanth, H; Willemson, BA; Jacobs, T; Sridhar, S
New Features in the Microwave Response of YBa 2 Cu 3 O 6.95 Crystals: Evidence for a Multicomponent Order Parameter Journal Article
In: arXiv preprint cond-mat/9610032, 1997.
@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 = {},
pubstate = {published},
tppubtype = {article}
}
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.
49.
Eskildsen, MR; Gammel, PL; Barber, BP; Yaron, U; Ramirez, AP; Huse, DA; Bishop, DJ; Bolle, C; Lieber, CM; Oxx, S; others,
Observation of a field-driven structural phase transition in the flux line lattice in ErNi 2 B 2 C Journal Article
In: Physical review letters, vol. 78, no. 10, pp. 1968, 1997.
@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 = {},
pubstate = {published},
tppubtype = {article}
}
50.
Srikanth, H; Willemsen, Balam A; Jacobs, T; Sridhar, S; Erb, A; Walker, E; Flükiger, R
Microwave response of YBa 2 Cu 3 O 6.95 crystals: Evidence for a multicomponent order parameter Journal Article
In: Physical Review B, vol. 55, no. 22, pp. R14733, 1997.
@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 = {},
pubstate = {published},
tppubtype = {article}
}
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.
51.
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.
@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 = {},
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 …
52.
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.
@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 = {},
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.
53.
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.
@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 = {},
pubstate = {published},
tppubtype = {article}
}
54.
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.
@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 = {},
pubstate = {published},
tppubtype = {article}
}
55.
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.
@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 = {},
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.
56.
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.
@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 = {},
pubstate = {published},
tppubtype = {article}
}
57.
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$$$$delta$$$$ films Journal Article
In: Physical Review, B: Condensed Matter, vol. 56, no. 18, 1997.
@article{willemsen1997criticalb,
title = {Critical-state flux penetration and linear microwave vortex response in YBa $$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 = {},
pubstate = {published},
tppubtype = {article}
}
58.
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.
@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 = {},
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 …
59.
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.
@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 = {},
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.
60.
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.
@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 = {},
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.
1989
28.
Kennedy, WL; Zahopoulos, C; Sridhar, S
Frequency-dependence of the microwave surface resistance of ceramic Y1Ba2Cu3Oy Journal Article
In: Solid state communications, vol. 70, no. 7, pp. 741–744, 1989.
Abstract | BibTeX | Tags: Superconductivity
@article{kennedy1989frequency,
title = {Frequency-dependence of the microwave surface resistance of ceramic Y1Ba2Cu3Oy},
author = {WL Kennedy and C Zahopoulos and S Sridhar},
year = {1989},
date = {1989-01-01},
journal = {Solid state communications},
volume = {70},
number = {7},
pages = {741--744},
publisher = {Pergamon},
abstract = {The frequency dependence of the surface resistance R3 of ceramic Y1Ba2Cu3Oy was measured between 5 GIIz and 20 GIIz in both the normal and superconducting states. The measurements were carried out using a fully superconducting resonant cavity made of the oxide superconductor. The surface resistance was found to vary as Rs ∝ fγ, with γ=0.6±0.2 at 118 K in the normal state, and γ=2.0±0.3 in the superconducting state. The normal state results are consistent in magnitude and frequency dependence with the classical skin effect, and the quadratic dependence in the superconducting state clearly indicates a local electrodynamics of a Josephson-coupled network.},
keywords = {Superconductivity},
pubstate = {published},
tppubtype = {article}
}
The frequency dependence of the surface resistance R3 of ceramic Y1Ba2Cu3Oy was measured between 5 GIIz and 20 GIIz in both the normal and superconducting states. The measurements were carried out using a fully superconducting resonant cavity made of the oxide superconductor. The surface resistance was found to vary as Rs ∝ fγ, with γ=0.6±0.2 at 118 K in the normal state, and γ=2.0±0.3 in the superconducting state. The normal state results are consistent in magnitude and frequency dependence with the classical skin effect, and the quadratic dependence in the superconducting state clearly indicates a local electrodynamics of a Josephson-coupled network.
1988
27.
Sridhar, S; Kennedy, WL
Novel technique to measure the microwave response of high T c superconductors between 4.2 and 200 K Journal Article
In: Review of scientific instruments, vol. 59, no. 4, pp. 531–536, 1988.
BibTeX | Tags: Superconductivity
@article{sridhar1988novel,
title = {Novel technique to measure the microwave response of high T c superconductors between 4.2 and 200 K},
author = {S Sridhar and WL Kennedy},
year = {1988},
date = {1988-01-01},
journal = {Review of scientific instruments},
volume = {59},
number = {4},
pages = {531--536},
publisher = {American Institute of Physics},
keywords = {Superconductivity},
pubstate = {published},
tppubtype = {article}
}
26.
Haldar, P; Sridhar, S; Roig-Janicki, A; Kennedy, W; Wu, DH; Zahopoulos, C; Giessen, BC
A new high-T c superconductor containing thallium and its crystal structure: The “1212” phase (Tl 1-x Bi x) 1.33 Sr 1.33 Ca 1.33 Cu 2 O 6.667+ $delta$ Journal Article
In: Journal of Superconductivity, vol. 1, no. 2, pp. 211–218, 1988.
BibTeX | Tags: Superconductivity
@article{haldar1988new,
title = {A new high-T c superconductor containing thallium and its crystal structure: The “1212” phase (Tl 1-x Bi x) 1.33 Sr 1.33 Ca 1.33 Cu 2 O 6.667+ $delta$},
author = {P Haldar and S Sridhar and A Roig-Janicki and W Kennedy and DH Wu and C Zahopoulos and BC Giessen},
year = {1988},
date = {1988-01-01},
journal = {Journal of Superconductivity},
volume = {1},
number = {2},
pages = {211--218},
publisher = {Kluwer Academic Publishers-Plenum Publishers},
keywords = {Superconductivity},
pubstate = {published},
tppubtype = {article}
}
25.
Sridhar, S
Rf and microwave experiments on Y 1 Ba 2 Cu 3 O/sub y/and La/sub 1.85/Sr/sub 0.15/CuO 4 Technical Report
1988.
Abstract | BibTeX | Tags: Superconductivity
@techreport{sridhar1988rf,
title = {Rf and microwave experiments on Y 1 Ba 2 Cu 3 O/sub y/and La/sub 1.85/Sr/sub 0.15/CuO 4},
author = {S Sridhar},
year = {1988},
date = {1988-01-01},
abstract = {The newly discovered high T/sub c/ superconductors have created tremendous interest, both as regards their fundamental properties and for possible applications at rf and microwave frequencies. The electromagnetic response of the 40K La/sub 2-x/Sr/sub x/CuO4 and the 93K RE1Ba2Cu3O/sub y/ (RE = Y, Er, Nd, Dy, Yb) superconductors over a very wide spectral range from rf to optical frequencies have been studied with two broad objectives. (1) Firstly, to understand the fundamental nature of the superconducting state, eg. is it the well-known BCS s-wave state or do we now have a fundamentally new type of superconductor? Electromagnetic probes are of particular significance for the high T/sub c/ superconductors, since they are sensitive only to the electronic state, unlike other traditional probes of the superconducting state such as ultrasonic attenuation or specific heat. The latter are strongly influenced by the phonon system, which is heavily populated at these high temperatures. (2) Secondly, to examine the potential of these materials for applications at rf, microwave and mm-wave frequencies. 10 references, 3 figures},
keywords = {Superconductivity},
pubstate = {published},
tppubtype = {techreport}
}
The newly discovered high T/sub c/ superconductors have created tremendous interest, both as regards their fundamental properties and for possible applications at rf and microwave frequencies. The electromagnetic response of the 40K La/sub 2-x/Sr/sub x/CuO4 and the 93K RE1Ba2Cu3O/sub y/ (RE = Y, Er, Nd, Dy, Yb) superconductors over a very wide spectral range from rf to optical frequencies have been studied with two broad objectives. (1) Firstly, to understand the fundamental nature of the superconducting state, eg. is it the well-known BCS s-wave state or do we now have a fundamentally new type of superconductor? Electromagnetic probes are of particular significance for the high T/sub c/ superconductors, since they are sensitive only to the electronic state, unlike other traditional probes of the superconducting state such as ultrasonic attenuation or specific heat. The latter are strongly influenced by the phonon system, which is heavily populated at these high temperatures. (2) Secondly, to examine the potential of these materials for applications at rf, microwave and mm-wave frequencies. 10 references, 3 figures
24.
Sridhar, S
Microwave response of thin-film superconductors Journal Article
In: Journal of applied physics, vol. 63, no. 1, pp. 159–166, 1988.
BibTeX | Tags: Superconductivity
@article{sridhar1988microwave,
title = {Microwave response of thin-film superconductors},
author = {S Sridhar},
year = {1988},
date = {1988-01-01},
journal = {Journal of applied physics},
volume = {63},
number = {1},
pages = {159--166},
publisher = {American Institute of Physics},
keywords = {Superconductivity},
pubstate = {published},
tppubtype = {article}
}
23.
Zahopoulos, C; Kennedy, WL; Sridhar, S
Performance of a fully superconducting microwave cavity made of the high T c superconductor Y1Ba2Cu3O y Journal Article
In: Applied physics letters, vol. 52, no. 25, pp. 2168–2170, 1988.
BibTeX | Tags: Superconductivity
@article{zahopoulos1988performance,
title = {Performance of a fully superconducting microwave cavity made of the high T c superconductor Y1Ba2Cu3O y},
author = {C Zahopoulos and WL Kennedy and S Sridhar},
year = {1988},
date = {1988-01-01},
journal = {Applied physics letters},
volume = {52},
number = {25},
pages = {2168--2170},
publisher = {American Institute of Physics},
keywords = {Superconductivity},
pubstate = {published},
tppubtype = {article}
}
22.
Wu, Dong-Ho; Shiffman, CA; Sridhar, S
Field variation of the penetration depth in ceramic Y 1 Ba 2 Cu 3 O y Journal Article
In: Physical Review B, vol. 38, no. 13, pp. 9311, 1988.
Abstract | BibTeX | Tags: Superconductivity
@article{wu1988field,
title = {Field variation of the penetration depth in ceramic Y 1 Ba 2 Cu 3 O y},
author = {Dong-Ho Wu and CA Shiffman and S Sridhar},
year = {1988},
date = {1988-01-01},
journal = {Physical Review B},
volume = {38},
number = {13},
pages = {9311},
publisher = {APS},
abstract = {The radio-frequency penetration depth is found to increase quadratically with applied dc magnetic field B, ie, Δ λ eff= k (T) B 2, between 4.2 and 85 K in samples of ceramic Y 1 Ba 2 Cu 3 O y. The parameter k (T) rises steeply with increasing temperature T, and even at 4.2 K is orders of magnitude larger than a Ginzburg-Landau prediction. Instead, the B 2 dependence and the large values of k can be quantitatively explained in terms of the dc flux dependence of the high-frequency response of a Josephson junction network, with typical junction area about 6 μ m 2. The analysis provides an explanation of the observed correspondence between λ eff (T), k (T), and the threshold field for irreversible flux entry.},
keywords = {Superconductivity},
pubstate = {published},
tppubtype = {article}
}
The radio-frequency penetration depth is found to increase quadratically with applied dc magnetic field B, ie, Δ λ eff= k (T) B 2, between 4.2 and 85 K in samples of ceramic Y 1 Ba 2 Cu 3 O y. The parameter k (T) rises steeply with increasing temperature T, and even at 4.2 K is orders of magnitude larger than a Ginzburg-Landau prediction. Instead, the B 2 dependence and the large values of k can be quantitatively explained in terms of the dc flux dependence of the high-frequency response of a Josephson junction network, with typical junction area about 6 μ m 2. The analysis provides an explanation of the observed correspondence between λ eff (T), k (T), and the threshold field for irreversible flux entry.
21.
Kennedy, WL; Sridhar, S
Low temperature microwave surface resistance of Y1Ba2Cu3Oy and La1. 85Sr0. 15CuO4 Journal Article
In: Solid state communications, vol. 68, no. 1, pp. 71–75, 1988.
Abstract | BibTeX | Tags: Superconductivity
@article{kennedy1988low,
title = {Low temperature microwave surface resistance of Y1Ba2Cu3Oy and La1. 85Sr0. 15CuO4},
author = {WL Kennedy and S Sridhar},
year = {1988},
date = {1988-01-01},
journal = {Solid state communications},
volume = {68},
number = {1},
pages = {71--75},
publisher = {Pergamon},
abstract = {Measurements of the microwave surface resistance Rδ at 9.58 GHz of polycrystalline Y1Ba2Cu3Oy and La1.85Sr0.15CuO4 over a wide range in temperature from 4.2 K to 100 K are reported. The temperature dependence of these materials are anomalous, over the entire temperature range, though very similar. Rδ is large at all temperatures, gradually decreasing by about 2 orders of magnitude from Tc to 4.2 K. The lowest values measured were Rδ(4.2 K) = 4.89×10−3 Ω for Y1Ba2Cu3Oy and 1.13×10−2 Ω for La1.85Sr0.15CuO4. Analysis of Rδ for an exponential temperature dependence at low temperatures does not indicate a clear and unique quasiparticle gap. We suggest that the highly anisotropic granularity of these materials may contribute strongly to the absorption mechanism.},
keywords = {Superconductivity},
pubstate = {published},
tppubtype = {article}
}
Measurements of the microwave surface resistance Rδ at 9.58 GHz of polycrystalline Y1Ba2Cu3Oy and La1.85Sr0.15CuO4 over a wide range in temperature from 4.2 K to 100 K are reported. The temperature dependence of these materials are anomalous, over the entire temperature range, though very similar. Rδ is large at all temperatures, gradually decreasing by about 2 orders of magnitude from Tc to 4.2 K. The lowest values measured were Rδ(4.2 K) = 4.89×10−3 Ω for Y1Ba2Cu3Oy and 1.13×10−2 Ω for La1.85Sr0.15CuO4. Analysis of Rδ for an exponential temperature dependence at low temperatures does not indicate a clear and unique quasiparticle gap. We suggest that the highly anisotropic granularity of these materials may contribute strongly to the absorption mechanism.
20.
Haldar, P; Roig-Janicki, A; Sridhar, S; Giessen, BC
A new intermediate-Tc oxide superconductor with a double perovskite structure: The “1-2-1” phase (Tl, Bi) 1 (Sr, Ca) 2Cu1O4. 5+ $delta$ Journal Article
In: Materials Letters, vol. 7, no. 1-2, pp. 1–4, 1988.
BibTeX | Tags: Superconductivity
@article{haldar1988newb,
title = {A new intermediate-Tc oxide superconductor with a double perovskite structure: The “1-2-1” phase (Tl, Bi) 1 (Sr, Ca) 2Cu1O4. 5+ $delta$},
author = {P Haldar and A Roig-Janicki and S Sridhar and BC Giessen},
year = {1988},
date = {1988-01-01},
journal = {Materials Letters},
volume = {7},
number = {1-2},
pages = {1--4},
publisher = {North-Holland},
keywords = {Superconductivity},
pubstate = {published},
tppubtype = {article}
}
19.
Haldar, P; Sridhar, S; Roig-Janicki, A; Kennedy, W; Wu, DH; Zahopoulos, C; Giessen, BC
New high-T/sub c/superconductor containing thallium and its crystal structure: the 1212 phase (Tl/sub 1-x/Bi/sub x/)/sub 1. 33/Sr/sub 1. 33/Ca/sub 1. 33/Cu/sub 2/O/sub 6. 67+ delta Journal Article
In: J. Superconduct.;(United States), vol. 1, no. 2, 1988.
Abstract | BibTeX | Tags: Superconductivity
@article{haldar1988newc,
title = {New high-T/sub c/superconductor containing thallium and its crystal structure: the 1212 phase (Tl/sub 1-x/Bi/sub x/)/sub 1. 33/Sr/sub 1. 33/Ca/sub 1. 33/Cu/sub 2/O/sub 6. 67+ delta},
author = {P Haldar and S Sridhar and A Roig-Janicki and W Kennedy and DH Wu and C Zahopoulos and BC Giessen},
year = {1988},
date = {1988-01-01},
journal = {J. Superconduct.;(United States)},
volume = {1},
number = {2},
publisher = {Northeastern Univ., Boston, MA (USA)},
abstract = {Joining YBa/sub 2/Cu/sub 3/O/sub 6.5 + delta/ (123 phase) and Bi/sub 4/Sr/sub 4/Ca/sub 2/Cu/sub 4/O/sub 16 + delta/ (4424 phase) as structurally characterized high-T/sub c/ superconductors, the thallium-containing superconductor (Tl/sub .75/Bi/sub .25/)/sub 1.33/Sr/sub 1.33/Ca/sub 1.33/Cu/sub 2/O/sub 6.67 + delta/ with the ideal stoichiometry (Tl, Bi)/sub 1/Sr/sub 2/Ca/sub 1/Cu/sub 2/O/sub 6.5 + delta/ (1212 phase) is reported here. As prepared from the component oxides, 1212 has an initial deviation from resistance linearity at 120 K, a superconducting onset temperature of 92 K, and zero resistance at 75 K. The tetragonal unit cell (P4/mmm, a = 3.800 /angstrom/; c = 12.072 /angstrom/, deduced from powder data) contains double copper oxygen sheets (like 4424 and 123) that alternate with single thallium-bismuth oxygen sheets (in contrast to 4424, which contains double bismuth oxygen sheets), resulting in a total of three stacked perovskite-like cells (as in 123). The copper oxide sheets (with intersheet spacing 3.38 /angstrom/) are separated by Ca/sup 2 +/ and the Cu oxide sheets and (Tl, Bi) oxide sheets (with spacing 4.35 /angstrom/) are separated by Sr/sup 2 +/, Ca/sup 2 +/, and excess (Tl, Bi)/sup 2 +/. The 1212 cell constitutes the building block for the centered, more complex 4424 cell.},
keywords = {Superconductivity},
pubstate = {published},
tppubtype = {article}
}
Joining YBa/sub 2/Cu/sub 3/O/sub 6.5 + delta/ (123 phase) and Bi/sub 4/Sr/sub 4/Ca/sub 2/Cu/sub 4/O/sub 16 + delta/ (4424 phase) as structurally characterized high-T/sub c/ superconductors, the thallium-containing superconductor (Tl/sub .75/Bi/sub .25/)/sub 1.33/Sr/sub 1.33/Ca/sub 1.33/Cu/sub 2/O/sub 6.67 + delta/ with the ideal stoichiometry (Tl, Bi)/sub 1/Sr/sub 2/Ca/sub 1/Cu/sub 2/O/sub 6.5 + delta/ (1212 phase) is reported here. As prepared from the component oxides, 1212 has an initial deviation from resistance linearity at 120 K, a superconducting onset temperature of 92 K, and zero resistance at 75 K. The tetragonal unit cell (P4/mmm, a = 3.800 /angstrom/; c = 12.072 /angstrom/, deduced from powder data) contains double copper oxygen sheets (like 4424 and 123) that alternate with single thallium-bismuth oxygen sheets (in contrast to 4424, which contains double bismuth oxygen sheets), resulting in a total of three stacked perovskite-like cells (as in 123). The copper oxide sheets (with intersheet spacing 3.38 /angstrom/) are separated by Ca/sup 2 +/ and the Cu oxide sheets and (Tl, Bi) oxide sheets (with spacing 4.35 /angstrom/) are separated by Sr/sup 2 +/, Ca/sup 2 +/, and excess (Tl, Bi)/sup 2 +/. The 1212 cell constitutes the building block for the centered, more complex 4424 cell.
18.
Shiffman, CA; Sridhar, S; Thomas, GE
Recent results of feasibility study to use the high T/sub c/oxide superconductors for microwave tube magnets Proceedings Article
In: Technical Digest., International Electron Devices Meeting, pp. 530–533, IEEE 1988.
Abstract | BibTeX | Tags: Superconductivity
@inproceedings{shiffman1988recent,
title = {Recent results of feasibility study to use the high T/sub c/oxide superconductors for microwave tube magnets},
author = {CA Shiffman and S Sridhar and GE Thomas},
year = {1988},
date = {1988-01-01},
booktitle = {Technical Digest., International Electron Devices Meeting},
pages = {530--533},
organization = {IEEE},
abstract = {The authors present results of a study to determine the feasibility of using high-T/sub c/ (90 K) ceramic superconductors in place of permanent magnet and conventional solenoids on microwave tubes. In the first phase of this work they developed a strategy based on persistent currents flowing in leadless, jointless configurations. In the present phase they focus on the possibilities and limitations of this design concept associated with the granular properties of the oxide superconductors in bulk ceramic form. They report measurements of the spatial distributions of the supercurrent density, excitation schemes, decay modes, long-term stabilities, and environmental degeneration in prototype ring magnets made from Y/sub 1/Ba/sub 2/Cu/sub 3/O/sub 7-x/. The prospects for practical microwave tube applications are discussed in the light of RF studies of granular superconductivity in this compound and recent advances in material preparation techniques.< >},
keywords = {Superconductivity},
pubstate = {published},
tppubtype = {inproceedings}
}
The authors present results of a study to determine the feasibility of using high-T/sub c/ (90 K) ceramic superconductors in place of permanent magnet and conventional solenoids on microwave tubes. In the first phase of this work they developed a strategy based on persistent currents flowing in leadless, jointless configurations. In the present phase they focus on the possibilities and limitations of this design concept associated with the granular properties of the oxide superconductors in bulk ceramic form. They report measurements of the spatial distributions of the supercurrent density, excitation schemes, decay modes, long-term stabilities, and environmental degeneration in prototype ring magnets made from Y/sub 1/Ba/sub 2/Cu/sub 3/O/sub 7-x/. The prospects for practical microwave tube applications are discussed in the light of RF studies of granular superconductivity in this compound and recent advances in material preparation techniques.< >
17.
Kennedy, WL; Sridhar, S
Low temperature microwave surface resistance of Y sub (1) Ba sub (2) Cu sub (3) O sub (y) and La sub (1. 85) Sr sub (0. 15) CuO sub (4). Journal Article
In: SOL. ST. COMMUN., vol. 68, no. 1, pp. 71–75, 1988.
Abstract | BibTeX | Tags: Superconductivity
@article{kennedy1988lowb,
title = {Low temperature microwave surface resistance of Y sub (1) Ba sub (2) Cu sub (3) O sub (y) and La sub (1. 85) Sr sub (0. 15) CuO sub (4).},
author = {WL Kennedy and S Sridhar},
year = {1988},
date = {1988-01-01},
journal = {SOL. ST. COMMUN.},
volume = {68},
number = {1},
pages = {71--75},
abstract = {Measurements of the microwave surface resistance R sub(s) at 9.58 GHz of polycrystalline Y sub(1)Ba sub(2)Cu sub(3)O sub(y) and La sub(1.85)Sr sub(0.15)CuO sub(4) over a wide range in temperature from 4.2 K to 100 K are reported. The temperature dependence of these materials are anomalous, over the entire temperature range, though very similar. R sub(s) is large at all temperatures, gradually decreasing by about 2 orders of magnitude from T sub(c) to 4.2 K. The lowest values measured were R sub(s)(4.2 K) = 4.89 x 10 super(-3) Omega for Y sub(1)Ba sub(2)Cu sub(3)O sub(y) and 1.13 x 10 super(-2) Omega for La sub(1.85)Sr sub(0.15)CuO sub(4). Analysis of R sub(s) for an exponential temperature dependence at low temperatures does not indicate a clear and unique quasiparticle gap.},
keywords = {Superconductivity},
pubstate = {published},
tppubtype = {article}
}
Measurements of the microwave surface resistance R sub(s) at 9.58 GHz of polycrystalline Y sub(1)Ba sub(2)Cu sub(3)O sub(y) and La sub(1.85)Sr sub(0.15)CuO sub(4) over a wide range in temperature from 4.2 K to 100 K are reported. The temperature dependence of these materials are anomalous, over the entire temperature range, though very similar. R sub(s) is large at all temperatures, gradually decreasing by about 2 orders of magnitude from T sub(c) to 4.2 K. The lowest values measured were R sub(s)(4.2 K) = 4.89 x 10 super(-3) Omega for Y sub(1)Ba sub(2)Cu sub(3)O sub(y) and 1.13 x 10 super(-2) Omega for La sub(1.85)Sr sub(0.15)CuO sub(4). Analysis of R sub(s) for an exponential temperature dependence at low temperatures does not indicate a clear and unique quasiparticle gap.
1987
16.
Sridhar, S; Shiffman, CA; Hamdeh, H
Electrodynamic response of Y 1 Ba 2 Cu 3 O y and La 1.85 Sr 0.15 Cu O 4- $delta$ in the superconducting state Journal Article
In: Physical Review B, vol. 36, no. 4, pp. 2301, 1987.
BibTeX | Tags: Superconductivity
@article{sridhar1987electrodynamic,
title = {Electrodynamic response of Y 1 Ba 2 Cu 3 O y and La 1.85 Sr 0.15 Cu O 4- $delta$ in the superconducting state},
author = {S Sridhar and CA Shiffman and H Hamdeh},
year = {1987},
date = {1987-01-01},
journal = {Physical Review B},
volume = {36},
number = {4},
pages = {2301},
publisher = {American Physical Society},
keywords = {Superconductivity},
pubstate = {published},
tppubtype = {article}
}
15.
Lu, YZ; Haldar, P; Markiewicz, R; Sridhar, S; Giessen, BC
Glassy Yb0. 17Ba0. 33Cu0. 50 alloy as precursor for the high-Tc oxide superconductor Y1Ba2Cu3Ox Journal Article
In: Materials Letters, vol. 5, no. 10, pp. 380–383, 1987.
Abstract | BibTeX | Tags: Superconductivity
@article{lu1987glassy,
title = {Glassy Yb0. 17Ba0. 33Cu0. 50 alloy as precursor for the high-Tc oxide superconductor Y1Ba2Cu3Ox},
author = {YZ Lu and P Haldar and R Markiewicz and S Sridhar and BC Giessen},
year = {1987},
date = {1987-01-01},
journal = {Materials Letters},
volume = {5},
number = {10},
pages = {380--383},
publisher = {North-Holland},
abstract = {We describe the preparation by rapid solidification processing (RSP), properties and alloy chemistry of the glassy alloy Yb0.17Ba0.33Cu0.50 and its oxidation to form the superconductor Yb1Ba2Cu3Ox with Tc = 93 K. Processing features and advantages of forming high-Tc superconductors via metallic alloy precursors are discussed.},
keywords = {Superconductivity},
pubstate = {published},
tppubtype = {article}
}
We describe the preparation by rapid solidification processing (RSP), properties and alloy chemistry of the glassy alloy Yb0.17Ba0.33Cu0.50 and its oxidation to form the superconductor Yb1Ba2Cu3Ox with Tc = 93 K. Processing features and advantages of forming high-Tc superconductors via metallic alloy precursors are discussed.
14.
Lu, YZ; Haldar, P; Markiewicz, R; Sridhar, S; Giessen, BC
Glassy Yb sub 0. 17 Ba sub 0. 33 Cu sub 0. 50 Alloy as Precursor for the High-T sub c Oxide Superconductor Yb sub 1 Ba sub 2 Cu sub 3 O sub x Journal Article
In: Mater. Lett., vol. 5, no. 10, pp. 380–383, 1987.
Abstract | BibTeX | Tags: Superconductivity
@article{lu1987glassyb,
title = {Glassy Yb sub 0. 17 Ba sub 0. 33 Cu sub 0. 50 Alloy as Precursor for the High-T sub c Oxide Superconductor Yb sub 1 Ba sub 2 Cu sub 3 O sub x},
author = {YZ Lu and P Haldar and R Markiewicz and S Sridhar and BC Giessen},
year = {1987},
date = {1987-01-01},
journal = {Mater. Lett.},
volume = {5},
number = {10},
pages = {380--383},
abstract = {The authors describe the preparation by rapid solidification processing (RSP), properties and alloy chemistry of the glassy alloy Yb/sub 0.17/Ba/sub 0.33/Cu/sub 0.50/and its oxidation to form the superconductor Yb/sub 1/Ba/sub 2/Cu/sub 3/O/sub x/with T/sub c/= 93 K. Processing features and advantages of forming high-T/sub c/superconductors via metallic alloy precursors are discussed. 16 refs.},
keywords = {Superconductivity},
pubstate = {published},
tppubtype = {article}
}
The authors describe the preparation by rapid solidification processing (RSP), properties and alloy chemistry of the glassy alloy Yb/sub 0.17/Ba/sub 0.33/Cu/sub 0.50/and its oxidation to form the superconductor Yb/sub 1/Ba/sub 2/Cu/sub 3/O/sub x/with T/sub c/= 93 K. Processing features and advantages of forming high-T/sub c/superconductors via metallic alloy precursors are discussed. 16 refs.
13.
Sridhar, S; Shiffman, CA; Hamdeh, H
Electrodynamic response of Y/sub 1/Ba/sub 2/Cu/sub 3/O/sub y/and La/sub 1. 85/Sr/sub 0. 15/CuO/sub 4-//sub delta/in the superconducting state Journal Article
In: Phys. Rev. B: Condens. Matter;(United States), vol. 36, no. 4, 1987.
Abstract | BibTeX | Tags: Superconductivity
@article{sridhar1987electrodynamicb,
title = {Electrodynamic response of Y/sub 1/Ba/sub 2/Cu/sub 3/O/sub y/and La/sub 1. 85/Sr/sub 0. 15/CuO/sub 4-//sub delta/in the superconducting state},
author = {S Sridhar and CA Shiffman and H Hamdeh},
year = {1987},
date = {1987-01-01},
journal = {Phys. Rev. B: Condens. Matter;(United States)},
volume = {36},
number = {4},
publisher = {Department of Physics, Northeastern University, Boston, Massachusetts 02115},
abstract = {Measurements of the temperature dependence of the surface resistance R/sub s/at 9.85 GHz and the screening length delta/sub s/at 1 MHz for the superconducting states of Y/sub 1/Ba/sub 2/Cu/sub 3/O/sub y/and La/sub 1.85/Sr/sub 0.15/CuO/sub 4/show strong correlations, suggesting that the superconducting state is the same in the two materials. While the overall temperature dependence of R/sub s/is reasonably well described by the Bardeen-Cooper-Schrieffer (BCS) theory in the very dirty limit, additional features are seen in R/sub s/and also in delta/sub s/which suggest detailed deviations from the BCS s-wave state.},
keywords = {Superconductivity},
pubstate = {published},
tppubtype = {article}
}
Measurements of the temperature dependence of the surface resistance R/sub s/at 9.85 GHz and the screening length delta/sub s/at 1 MHz for the superconducting states of Y/sub 1/Ba/sub 2/Cu/sub 3/O/sub y/and La/sub 1.85/Sr/sub 0.15/CuO/sub 4/show strong correlations, suggesting that the superconducting state is the same in the two materials. While the overall temperature dependence of R/sub s/is reasonably well described by the Bardeen-Cooper-Schrieffer (BCS) theory in the very dirty limit, additional features are seen in R/sub s/and also in delta/sub s/which suggest detailed deviations from the BCS s-wave state.
12.
Sridhar, S; Shiffman, CA; Hamdeh, H
Electrodynamic response of Y1Ba2Cu3Oy and La1. 85Sr0. 15CuO4-delta in the superconducting state Journal Article
In: Physical Review B, vol. 36, pp. 2301–2304, 1987.
Abstract | BibTeX | Tags: Superconductivity
@article{sridhar1987electrodynamicc,
title = {Electrodynamic response of Y1Ba2Cu3Oy and La1. 85Sr0. 15CuO4-delta in the superconducting state},
author = {S Sridhar and CA Shiffman and H Hamdeh},
year = {1987},
date = {1987-01-01},
journal = {Physical Review B},
volume = {36},
pages = {2301--2304},
abstract = {Measurements of the temperature dependence of the surface resistance R s at 9.85 GHz and the screening length delta s at 1 MHz for the superconducting states of Y 1 Ba 2 Cu 3 O y and La 1.85 Sr 0.15 CuO 4 show strong correlations, suggesting that the superconducting state is the same in the two materials. While the overall temperature dependence of R s is reasonably well described by the Bardeen-Cooper-Schrieffer (BCS) theory in the very dirty limit, additional features are seen in R s and also in delta s which suggest detailed deviations from the BCS s-wave state.},
keywords = {Superconductivity},
pubstate = {published},
tppubtype = {article}
}
Measurements of the temperature dependence of the surface resistance R s at 9.85 GHz and the screening length delta s at 1 MHz for the superconducting states of Y 1 Ba 2 Cu 3 O y and La 1.85 Sr 0.15 CuO 4 show strong correlations, suggesting that the superconducting state is the same in the two materials. While the overall temperature dependence of R s is reasonably well described by the Bardeen-Cooper-Schrieffer (BCS) theory in the very dirty limit, additional features are seen in R s and also in delta s which suggest detailed deviations from the BCS s-wave state.
1984
11.
Sridhar, Srinivas
Microwave dynamics of quasiparticles and critical fields in superconducting films. Journal Article
In: 1984.
Abstract | BibTeX | Tags: Superconductivity
@article{sridhar1984microwave,
title = {Microwave dynamics of quasiparticles and critical fields in superconducting films.},
author = {Srinivas Sridhar},
year = {1984},
date = {1984-01-01},
abstract = {The microwave response of the superconducting state in equilibrium and non-equilibrium configurations was examined experimentally and analytically. Thin film superconductors were mostly studied in order to explore spatial effects. The response parameter measured was the surface impedance.},
keywords = {Superconductivity},
pubstate = {published},
tppubtype = {article}
}
The microwave response of the superconducting state in equilibrium and non-equilibrium configurations was examined experimentally and analytically. Thin film superconductors were mostly studied in order to explore spatial effects. The response parameter measured was the surface impedance.
1983
10.
SRIDHAR, S
Microwave dynamics of quasiparticles and critical fields in superconducting films[Ph. D. Thesis] Journal Article
In: 1983.
Abstract | BibTeX | Tags: Superconductivity
@article{sridhar1983microwave,
title = {Microwave dynamics of quasiparticles and critical fields in superconducting films[Ph. D. Thesis]},
author = {S SRIDHAR},
year = {1983},
date = {1983-01-01},
abstract = {The microwave response of the superconducting state in equilibrium and non-equilibrium configurations was examined experimentally and analytically. Thin film superconductors were mostly studied in order to explore spatial effects. The response parameter measured was the surface impedance. For small microwave intensity the surface impedance at 10 GHz was measured for a variety of samples (mostly Sn) over a wide range of sample thickness and temperature. A detailed analysis based on the BCS theory was developed for calculating the surface impedance for general thickness and other experimental parameters. Experiment and theory agreed with each other to within the experimental accuracy. Thus it was established that the samples, thin films as well as bulk, were well characterized at low microwave powers (near equilibrium).},
keywords = {Superconductivity},
pubstate = {published},
tppubtype = {article}
}
The microwave response of the superconducting state in equilibrium and non-equilibrium configurations was examined experimentally and analytically. Thin film superconductors were mostly studied in order to explore spatial effects. The response parameter measured was the surface impedance. For small microwave intensity the surface impedance at 10 GHz was measured for a variety of samples (mostly Sn) over a wide range of sample thickness and temperature. A detailed analysis based on the BCS theory was developed for calculating the surface impedance for general thickness and other experimental parameters. Experiment and theory agreed with each other to within the experimental accuracy. Thus it was established that the samples, thin films as well as bulk, were well characterized at low microwave powers (near equilibrium).
1981
9.
Mercereau, JE; Sridhar, S
MICROWAVE SURFACE IMPEDANCE OF THIN-FILM SUPERCONDUCTORS Proceedings Article
In: BULLETIN OF THE AMERICAN PHYSICAL SOCIETY, pp. 308–308, AMER INST PHYSICS CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY~… 1981.
BibTeX | Tags: Superconductivity
@inproceedings{mercereau1981microwave,
title = {MICROWAVE SURFACE IMPEDANCE OF THIN-FILM SUPERCONDUCTORS},
author = {JE Mercereau and S Sridhar},
year = {1981},
date = {1981-01-01},
booktitle = {BULLETIN OF THE AMERICAN PHYSICAL SOCIETY},
volume = {26},
number = {3},
pages = {308--308},
organization = {AMER INST PHYSICS CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY~…},
keywords = {Superconductivity},
pubstate = {published},
tppubtype = {inproceedings}
}
1980
8.
SRIDHAR, S; MERCEREAU, JE
NON-EQUILIBRIUM EFFECTS ON THE SURFACE IMPEDANCE OF THIN-FILM SUPERCONDUCTORS Proceedings Article
In: BULLETIN OF THE AMERICAN PHYSICAL SOCIETY, pp. 412–412, AMER INST PHYSICS CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY~… 1980.
BibTeX | Tags: Superconductivity
@inproceedings{sridhar1980non,
title = {NON-EQUILIBRIUM EFFECTS ON THE SURFACE IMPEDANCE OF THIN-FILM SUPERCONDUCTORS},
author = {S SRIDHAR and JE MERCEREAU},
year = {1980},
date = {1980-01-01},
booktitle = {BULLETIN OF THE AMERICAN PHYSICAL SOCIETY},
volume = {25},
number = {3},
pages = {412--412},
organization = {AMER INST PHYSICS CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY~…},
keywords = {Superconductivity},
pubstate = {published},
tppubtype = {inproceedings}
}
7.
Sridhar, S; Mercereau, JE
Effects of quasiparticle redistribution on the surface impedance of superconductors Journal Article
In: Physics Letters A, vol. 75, no. 5, pp. 392–394, 1980.
Abstract | BibTeX | Tags: Superconductivity
@article{sridhar1980effects,
title = {Effects of quasiparticle redistribution on the surface impedance of superconductors},
author = {S Sridhar and JE Mercereau},
year = {1980},
date = {1980-01-01},
journal = {Physics Letters A},
volume = {75},
number = {5},
pages = {392--394},
publisher = {Elsevier},
abstract = {Calculations of surface impedance of a thin film superconductor indicate a significant decrease, with increasing microwave power, due to quasiparticle redistribution. An expression for the microwave-to-film coupling is derived. The distribution function is solved self-consistently to avoid a singularity.},
keywords = {Superconductivity},
pubstate = {published},
tppubtype = {article}
}
Calculations of surface impedance of a thin film superconductor indicate a significant decrease, with increasing microwave power, due to quasiparticle redistribution. An expression for the microwave-to-film coupling is derived. The distribution function is solved self-consistently to avoid a singularity.
1979
6.
Sridhar, S; Mercereau, JE
EFFECTS OF NON-EQUILIBRIUM QUASIPARTICLES ON THE SURFACE IMPEDANCE OF SUPERCONDUCTORS Proceedings Article
In: BULLETIN OF THE AMERICAN PHYSICAL SOCIETY, pp. 330–330, AMER INST PHYSICS CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY~… 1979.
BibTeX | Tags: Superconductivity
@inproceedings{sridhar1979effects,
title = {EFFECTS OF NON-EQUILIBRIUM QUASIPARTICLES ON THE SURFACE IMPEDANCE OF SUPERCONDUCTORS},
author = {S Sridhar and JE Mercereau},
year = {1979},
date = {1979-01-01},
booktitle = {BULLETIN OF THE AMERICAN PHYSICAL SOCIETY},
volume = {24},
number = {3},
pages = {330--330},
organization = {AMER INST PHYSICS CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY~…},
keywords = {Superconductivity},
pubstate = {published},
tppubtype = {inproceedings}
}
1977
5.
Zahopoulos, C; Sridhar, S; Lanagan, M
PERFORMANCE OF A high T. SUPERCONDUCTING ULTRA-Low LOSS Proceedings Article
In: Technology 2001: Conference Proceedings: the Second National Technology Transfer Conference and Exposition, December 3-5, 1991, San Jose Convention Center, San Jose, CA., pp. 232, Scientific and Technical Information Office, National Aeronautics and Space~… 1977.
Abstract | BibTeX | Tags: Superconductivity
@inproceedings{zahopoulos1977performance,
title = {PERFORMANCE OF A high T. SUPERCONDUCTING ULTRA-Low LOSS},
author = {C Zahopoulos and S Sridhar and M Lanagan},
year = {1977},
date = {1977-01-01},
booktitle = {Technology 2001: Conference Proceedings: the Second National Technology Transfer Conference and Exposition, December 3-5, 1991, San Jose Convention Center, San Jose, CA.},
volume = {2},
number = {3136},
pages = {232},
organization = {Scientific and Technical Information Office, National Aeronautics and Space~…},
abstract = {This article reports successful fabrication of a five-pole interdigital stripline filter made of the 93-K superconductor (Yi BajCu3O,) coated on a silver substrate, with center frequency of 8.5 GHz and an extremely high rejection ratio of 80 dB. The lowest insertion 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 criticaltemperature filters. The insertion loss appears to be limited by extrinsic factors, such as tuning mismatch and joint losses, and not by the superconducting material losses.},
keywords = {Superconductivity},
pubstate = {published},
tppubtype = {inproceedings}
}
This article reports successful fabrication of a five-pole interdigital stripline filter made of the 93-K superconductor (Yi BajCu3O,) coated on a silver substrate, with center frequency of 8.5 GHz and an extremely high rejection ratio of 80 dB. The lowest insertion 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 criticaltemperature filters. The insertion loss appears to be limited by extrinsic factors, such as tuning mismatch and joint losses, and not by the superconducting material losses.
1976
4.
MILLS, NG; SRIDHAR, S; WILKES, KE
ROLE OF CONDUCTION ELECTRONS IN KAPITZA BOUNDARY CONDUCTANCE Proceedings Article
In: BULLETIN OF THE AMERICAN PHYSICAL SOCIETY, pp. 352–352, AMER INST PHYSICS CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY~… 1976.
BibTeX | Tags: Superconductivity
@inproceedings{mills1976role,
title = {ROLE OF CONDUCTION ELECTRONS IN KAPITZA BOUNDARY CONDUCTANCE},
author = {NG MILLS and S SRIDHAR and KE WILKES},
year = {1976},
date = {1976-01-01},
booktitle = {BULLETIN OF THE AMERICAN PHYSICAL SOCIETY},
volume = {21},
number = {3},
pages = {352--352},
organization = {AMER INST PHYSICS CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY~…},
keywords = {Superconductivity},
pubstate = {published},
tppubtype = {inproceedings}
}
0000
3.
Jacobs, T; Sridhar, S; Li, Qiang; Gu, GD; Koshizuka, N
In-Plane and ˆc-Axis Microwave Penetration Depth of Bi2Sr2Ca1Cu2O81d Crystals Journal Article
In: 0000.
Abstract | BibTeX | Tags: Superconductivity
@article{jacobsplane,
title = {In-Plane and ˆc-Axis Microwave Penetration Depth of Bi2Sr2Ca1Cu2O81d Crystals},
author = {T Jacobs and S Sridhar and Qiang Li and GD Gu and N Koshizuka},
abstract = {The complete temperature dependences of the in-plane and ˆc-axis microwave (10 GHz) penetration depth l (T) and the surface resistance Rs (T) of high quality Bi2Sr2Ca1Cu2O81d crystals are reported. In contrast to earlier measurements, a leading lab~ T dependence is observed at low temperatures, consistent with nodes in the in-plane gap. The overall behavior of lab (T) and Rs ab (T) is similar to that of YBa2Cu3Oy at low T, but differs at temperatures near Tc. The ˆc-axis penetration depth lc (T) is shown to best agree with a model of weakly coupled superconducting layers with nodes in the gap.
},
keywords = {Superconductivity},
pubstate = {published},
tppubtype = {article}
}
The complete temperature dependences of the in-plane and ˆc-axis microwave (10 GHz) penetration depth l (T) and the surface resistance Rs (T) of high quality Bi2Sr2Ca1Cu2O81d crystals are reported. In contrast to earlier measurements, a leading lab~ T dependence is observed at low temperatures, consistent with nodes in the in-plane gap. The overall behavior of lab (T) and Rs ab (T) is similar to that of YBa2Cu3Oy at low T, but differs at temperatures near Tc. The ˆc-axis penetration depth lc (T) is shown to best agree with a model of weakly coupled superconducting layers with nodes in the gap.
2.
Kennedy, WL; Zahopoulos, C; Sridhar, S
li. EQUENCY-UEPENDENCE OF THE MICROWAVE SURFACE RESISTANCE OF CERAMIC У, Вп2Си30 „ Journal Article
In: 0000.
Abstract | BibTeX | Tags: Superconductivity
@article{kennedyli,
title = {li. EQUENCY-UEPENDENCE OF THE MICROWAVE SURFACE RESISTANCE OF CERAMIC У, Вп2Си30 „},
author = {WL Kennedy and C Zahopoulos and S Sridhar},
abstract = {The frequency dependence оГ the surface resistance Rj of ceramic Y^ BaaGujÓgv; ik measured between 5 GHz and 20 GJlz in both the normal a. nd superconducting states. Tlie measurements were carried out using a, fully superconducting resonant cavity T made of the oxide superconductor. The surface resistance was found to vary as R, к f, with 7= 0.0±0.2 at 118 1С in the normal state, and у= 2.0±0.3 in the superconducting state. The normal stale results are consistent in magnitude and frequency dependence with the classical skin effect, and the quadratic dependence in the superconducting state clearly indicates a local electrodynamics оГ a Josephson-coupled network.
The microwave response of the recently discovered oxide superconductors is of considerable interest, both from a fundamental scientific and technological viewpoint. Several measurements of the temperature dependence of the surface …},
keywords = {Superconductivity},
pubstate = {published},
tppubtype = {article}
}
The frequency dependence оГ the surface resistance Rj of ceramic Y^ BaaGujÓgv; ik measured between 5 GHz and 20 GJlz in both the normal a. nd superconducting states. Tlie measurements were carried out using a, fully superconducting resonant cavity T made of the oxide superconductor. The surface resistance was found to vary as R, к f, with 7= 0.0±0.2 at 118 1С in the normal state, and у= 2.0±0.3 in the superconducting state. The normal stale results are consistent in magnitude and frequency dependence with the classical skin effect, and the quadratic dependence in the superconducting state clearly indicates a local electrodynamics оГ a Josephson-coupled network.
The microwave response of the recently discovered oxide superconductors is of considerable interest, both from a fundamental scientific and technological viewpoint. Several measurements of the temperature dependence of the surface …
The microwave response of the recently discovered oxide superconductors is of considerable interest, both from a fundamental scientific and technological viewpoint. Several measurements of the temperature dependence of the surface …
1.
Kusko, C; Zhai, Z; Markiewicz, RS; Sridhar, S
Publication: Journal of Superconductivity Pub Date: 2001 Journal Article
In: 0000.
BibTeX | Tags: Superconductivity
@article{kuskopublication,
title = {Publication: Journal of Superconductivity Pub Date: 2001},
author = {C Kusko and Z Zhai and RS Markiewicz and S Sridhar},
keywords = {Superconductivity},
pubstate = {published},
tppubtype = {article}
}
