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1993
Sridhar, S
Quantum Dynamics of Chaotic Systems Journal Article
In: 1993.
BibTeX | Tags: Quantum Chaos
@article{sridhar1993quantum,
title = {Quantum Dynamics of Chaotic Systems},
author = {S Sridhar},
year = {1993},
date = {1993-01-01},
publisher = {Gordon and Breach, Amsterdam},
keywords = {Quantum Chaos},
pubstate = {published},
tppubtype = {article}
}
Sridhar, S; Hogenboom, D; Kudrolli, A
Exper-imental eigenvalue spectra of “rough” and multiplyconnected billiards,” Journal Article
In: Quantum Dynamics of Chaotic Systems, eds. Yuan, JM, Feng, DH & Zaslavsky, GM (Gordon and Breach, Amsterdam), pp. 297–304, 1993.
Abstract | BibTeX | Tags: Quantum Chaos
@article{sridhar1993exper,
title = {Exper-imental eigenvalue spectra of “rough” and multiplyconnected billiards,”},
author = {S Sridhar and D Hogenboom and A Kudrolli},
year = {1993},
date = {1993-01-01},
journal = {Quantum Dynamics of Chaotic Systems, eds. Yuan, JM, Feng, DH & Zaslavsky, GM (Gordon and Breach, Amsterdam)},
pages = {297--304},
abstract = {We use microwave cavities to study the spectra of billiards with" rough" perimeters, or which ara multiply connected-While simple boundaries show cumulative level densities N (E) which are in good agreement with the Weyl formula, qualitative departures are observed at low energies-when the perimeter is" roughened" by increasing the ratio of perimeter L to area A, and when obstacles are introduced to make the billiard multiply connected. Thus the Weyl formula even including perimeter corrections is not a good yardstick at low energies which probe internal length scales, interestingly, in the case of a multiply-connected billiard with a periodic array of obstacles, large" gaps" are observed in the discrete spectrum, somewhat like a solid-state lattice of finite size. The gaps persist when disorder¿ î introduced, Le. in the analog of a solid-state glass.
The influence of the shape of a planar domain on the eigenvalue …},
keywords = {Quantum Chaos},
pubstate = {published},
tppubtype = {article}
}
The influence of the shape of a planar domain on the eigenvalue …
Wei, Yan-Zhen; Sridhar, S
Relationships between the dielectric and structural properties of supercooled LiCl: RH2O solutions Journal Article
In: Journal of Molecular Liquids, vol. 56, pp. 259–273, 1993.
Abstract | BibTeX | Tags: Chemical & Biological Physics
@article{wei1993relationships,
title = {Relationships between the dielectric and structural properties of supercooled LiCl: RH2O solutions},
author = {Yan-Zhen Wei and S Sridhar},
year = {1993},
date = {1993-01-01},
journal = {Journal of Molecular Liquids},
volume = {56},
pages = {259--273},
publisher = {Elsevier},
abstract = {The relation between the dynamics of dielectric relaxation, the glass-forming ability and properties in the supercooled state of LiCl:RH2O solutions are investigated, via measurements of the dielectric spectra between 45 MHz and 20 GHz and temperatures between 210 K and 300 K and concentrations R ≤ 20. For high concentration glass-forming solutions, a close correspondence between the temperature dependencies of the Cole-Cole relaxation time τC, the conductivity, and the viscosity, is observed. τC(T) is well-described by a power law form (T-TMC)γ, with TMC ∼ 205 K and γ ∼ 2, a form motivated by mode-coupling theory. The data suggest that non-Debye response at room temperature is associated with the ability to vitrify at low temperatures. A microscopic basis for the avoidance of crystallization is provided by obtaining from the dielectric data the mean radius available to a water molecule, which is shown to approach 1.9 Å in the highly concentrated solutions. This suggests strong confinement of water molecules by the ions, which prevents macroscopic crystallization from occurring when cooled.},
keywords = {Chemical & Biological Physics},
pubstate = {published},
tppubtype = {article}
}
1992
Sridhar, S; Heller, EJ
Physical and numerical experiments on the wave mechanics of classically chaotic systems Journal Article
In: Physical Review A, vol. 46, no. 4, pp. R1728, 1992.
Abstract | BibTeX | Tags: Quantum Chaos
@article{sridhar1992physical,
title = {Physical and numerical experiments on the wave mechanics of classically chaotic systems},
author = {S Sridhar and EJ Heller},
year = {1992},
date = {1992-01-01},
journal = {Physical Review A},
volume = {46},
number = {4},
pages = {R1728},
publisher = {American Physical Society},
abstract = {We study chaotic quantum billiards using both microwave cavities and numerical simulations. For the same geometry, viz., a Sinai billiard, agreement to remarkable precision is found for both the eigenvalue magnitudes and the spatial detail of the eigenfunctions. The association of the eigenfunctions with classical periodic orbits is demonstrated, and scarred states are identified. Desymmetrizing the Sinai billiard by slightly moving the central disk is shown to lead to strong localization of the eigenfunction. The calculated eigenstates of the symmetric billiard show an even-and odd-parity pair whose linear combination gives the localized state.},
keywords = {Quantum Chaos},
pubstate = {published},
tppubtype = {article}
}
Owliaei, J; Sridhar, S; Talvacchio, J
Field-dependent crossover in the vortex response at microwave frequencies in YBa 2 Cu 3 O 7- $delta$ films Journal Article
In: Physical review letters, vol. 69, no. 23, pp. 3366, 1992.
BibTeX | Tags: Superconductivity
@article{owliaei1992field,
title = {Field-dependent crossover in the vortex response at microwave frequencies in YBa 2 Cu 3 O 7- $delta$ films},
author = {J Owliaei and S Sridhar and J Talvacchio},
year = {1992},
date = {1992-01-01},
journal = {Physical review letters},
volume = {69},
number = {23},
pages = {3366},
publisher = {American Physical Society},
keywords = {Superconductivity},
pubstate = {published},
tppubtype = {article}
}
Sridhar, S; Hogenboom, DO; Willemsen, Balam A
Microwave experiments on chaotic billiards Journal Article
In: Journal of statistical physics, vol. 68, no. 1-2, pp. 239–258, 1992.
Abstract | BibTeX | Tags: Quantum Chaos
@article{sridhar1992microwave,
title = {Microwave experiments on chaotic billiards},
author = {S Sridhar and DO Hogenboom and Balam A Willemsen},
year = {1992},
date = {1992-01-01},
journal = {Journal of statistical physics},
volume = {68},
number = {1-2},
pages = {239--258},
publisher = {Kluwer Academic Publishers-Plenum Publishers},
abstract = {We describe experiments using billiard-shaped microwave cavities, to test ideas in quantum chaos. The experimental method for observing cavity resonances to obtain the eigenvalues, and the advantages and limitations of the techniques, including the influence of absorption, are discussed. An experimental technique to obtain a 2D mapping of the wavefunction is described. Results are displayed for 36 of the low-lying wavefunctions of a Sinai billiard cavity consisting of a central disc in a rectangular enclosure. The wavefunctions demonstrate the influence of classical periodic orbits (PO), of which there are two types: non-isolated PO, which avoid the central disc, and isolated PO, which hit the central disc. Scarred states, including those associated with isolated PO, are directly observed.},
keywords = {Quantum Chaos},
pubstate = {published},
tppubtype = {article}
}
Wei, Yan-Zhen; Chiang, Ping; Sridhar, S
Ion size effects on the dynamic and static dielectric properties of aqueous alkali solutions Journal Article
In: The Journal of chemical physics, vol. 96, no. 6, pp. 4569–4573, 1992.
Abstract | BibTeX | Tags: Chemical & Biological Physics
@article{wei1992ion,
title = {Ion size effects on the dynamic and static dielectric properties of aqueous alkali solutions},
author = {Yan-Zhen Wei and Ping Chiang and S Sridhar},
year = {1992},
date = {1992-01-01},
journal = {The Journal of chemical physics},
volume = {96},
number = {6},
pages = {4569--4573},
publisher = {American Institute of Physics},
abstract = {Dielectric spectroscopy studies of aqueous ionic solutions ACl/H2O (A=Li, Rb, Cs) were carried out at frequencies between 45 MHz and 20 GHz, using recently developed coaxial measurement techniques. The behavior of the static dielectric constant εs0 and the dielectric relaxation time τD of the solutions were studied as functions of ion size and concentration. For moderate concentrations both εs0 and τD decrease linearly with solution conductivity. While the behavior of εs0 can be understood in terms of either static or Hubbard–Onsager kinetic polarization models, the experimental results for τD are at present not understood quantitatively in terms of these models. However we point out the good correlation of the τD data with empirical viscosity results, which suggests an alternative explanation based upon the solution viscosity, modified by ion size effects, which play an important role in the dielectric response. We also discuss the various length scales relevant to dielectric and conductivity processes in the solutions.},
keywords = {Chemical & Biological Physics},
pubstate = {published},
tppubtype = {article}
}
Sridhar, S; Maheswaran, B; Willemsen, Balam A; Wu, Dong Ho; Haddon, RC
Scaling behavior of the rf vortex penetration depth in an organic superconductor Journal Article
In: Physical review letters, vol. 68, no. 14, pp. 2220, 1992.
Abstract | BibTeX | Tags: Superconductivity
@article{sridhar1992scaling,
title = {Scaling behavior of the rf vortex penetration depth in an organic superconductor},
author = {S Sridhar and B Maheswaran and Balam A Willemsen and Dong Ho Wu and RC Haddon},
year = {1992},
date = {1992-01-01},
journal = {Physical review letters},
volume = {68},
number = {14},
pages = {2220},
publisher = {APS},
abstract = {The radiofrequency penetration depth λ (H, T) of the organic superconductor (BEDT-TTF) 2 Cu (NCS) 2 was studied in the mixed state at moderate fields. The data can be scaled into a single functional form Δλ (H, T)= Δ λ*(T) f (H/H*(T)), where H*(T)×(1-t) 3/2/t can be identified with a ‘‘depinning’’or ‘‘irreversibility’’line. We show that the scaling features are contained in a theory of vortex motion in a periodic pootential under the influence of thermal fluctuations, which describes the functional form quantitatively. The data for Δλ (H= 0, T) are governed by the same (vortex) length scale as the finite-field data, suggesting that the zero-field state is not a conventional Meissner state obeying a London relation.},
keywords = {Superconductivity},
pubstate = {published},
tppubtype = {article}
}
Rath, S; Sridhar, S
Core instability of elliptic drift vortices Journal Article
In: Physics of Fluids B: Plasma Physics, vol. 4, no. 5, pp. 1367–1369, 1992.
Abstract | BibTeX | Tags: Superconductivity
@article{rath1992core,
title = {Core instability of elliptic drift vortices},
author = {S Rath and S Sridhar},
year = {1992},
date = {1992-01-01},
journal = {Physics of Fluids B: Plasma Physics},
volume = {4},
number = {5},
pages = {1367--1369},
publisher = {American Institute of Physics},
abstract = {It is shown that two‐dimensional drift vortices with elliptic cores are unstable to certain short‐wavelength three‐dimensional perturbations. Circular vortices are stable to those modes. At short wavelengths, the growth rate is independent of the wavelength and, for small ellipticity, it is proportional to the ellipticity.},
keywords = {Superconductivity},
pubstate = {published},
tppubtype = {article}
}
Wei, Yanzhen; Sridhar, S
Biological applications of a technique for broadband complex permittivity measurements Proceedings Article
In: 1992 IEEE MTT-S Microwave Symposium Digest, pp. 1271–1274, IEEE 1992.
Abstract | BibTeX | Tags: Chemical & Biological Physics
@inproceedings{wei1992biological,
title = {Biological applications of a technique for broadband complex permittivity measurements},
author = {Yanzhen Wei and S Sridhar},
year = {1992},
date = {1992-01-01},
booktitle = {1992 IEEE MTT-S Microwave Symposium Digest},
pages = {1271--1274},
organization = {IEEE},
abstract = {A broadband coax technique developed for the measurement of dielectric properties of biological substances up to at least 20 GHz is discussed. For water-based materials such as blood or muscle substitute phantoms, a 0.047 inch size probe is essential to minimize errors due to radiation. The data indicate the importance of dielectric volume of the constituents, and enable tailoring of phantoms and substitutes for use in biomedical applications.< >},
keywords = {Chemical & Biological Physics},
pubstate = {published},
tppubtype = {inproceedings}
}
Liu, Ping; Rappaport, Carey M; Wei, Yan-zhen; Sridhar, S
Simulated biological materials at microwave frequencies for the study of electromagnetic hyperthermia Proceedings Article
In: 1992 14th Annual International Conference of the IEEE Engineering in Medicine and Biology Society, pp. 272–273, IEEE 1992.
Abstract | BibTeX | Tags: Chemical & Biological Physics
@inproceedings{liu1992simulated,
title = {Simulated biological materials at microwave frequencies for the study of electromagnetic hyperthermia},
author = {Ping Liu and Carey M Rappaport and Yan-zhen Wei and S Sridhar},
year = {1992},
date = {1992-01-01},
booktitle = {1992 14th Annual International Conference of the IEEE Engineering in Medicine and Biology Society},
volume = {1},
pages = {272--273},
organization = {IEEE},
abstract = {For the study of electromagnetic hyperthermia, it is necessary to simulate human biological materials in microwave frequencies. Using a new technique for the precise measurement of the dielectric properties of the simulated materials for frequencies up to 20 GHz, we have modified the previous simulation for high water content tissue at the frequency range 100-1000 MHz. We present new formulas for the frequency range 5-20 GHz. Modifications of composition for various frequencies are discussed.},
keywords = {Chemical & Biological Physics},
pubstate = {published},
tppubtype = {inproceedings}
}
Sridhar, S
EM Properties of High Tc Superconductors Technical Report
DTIC Document 1992.
Abstract | BibTeX | Tags: Superconductivity
@techreport{sridhar1992properties,
title = {EM Properties of High Tc Superconductors},
author = {S Sridhar},
year = {1992},
date = {1992-01-01},
institution = {DTIC Document},
abstract = {The aim of this contract was to study the factors influencing microwave properties9 of high1 TrV smiperconductuirs, via fundamental measurements on high quality thin film and s;ingle- cryqta1 material,~. Two principal lines of investigation were pursued: Tn single crystals of Y1BaCuOQ>5 (Tc=93K) ultrasensitive rf methods were used to study the penetration depth X, lower critical fields Hc1 and vortex pinning forces. The i penetration depth and surf. ace resistance were found to obey temperature dependencesi good agreemont with BCS calculations. The anisotropy and temperature dependence of
Itwere measured and also found to tie in good agreement with 13CS theory. The
pinning forrc'o were measured, and the results imply that In good quality single
crystals, tht. pinning is due to core pinning by defects, and implies intrinsic
critical currents 2x10'A/cM2.},
keywords = {Superconductivity},
pubstate = {published},
tppubtype = {techreport}
}
Itwere measured and also found to tie in good agreement with 13CS theory. The
pinning forrc'o were measured, and the results imply that In good quality single
crystals, tht. pinning is due to core pinning by defects, and implies intrinsic
critical currents 2x10'A/cM2.
1991
Sridhar, S
Experimental observation of scarred eigenfunctions of chaotic microwave cavities Journal Article
In: Physical review letters, vol. 67, no. 7, pp. 785, 1991.
Abstract | BibTeX | Tags: Chemical & Biological Physics
@article{sridhar1991experimental,
title = {Experimental observation of scarred eigenfunctions of chaotic microwave cavities},
author = {S Sridhar},
year = {1991},
date = {1991-01-01},
journal = {Physical review letters},
volume = {67},
number = {7},
pages = {785},
publisher = {APS},
abstract = {The wave functions of Sinai-billiard-shaped microwave cavities are experimentally studied. Some of the general features observed are parity breaking in the lowest eigenstates,‘‘bouncing-ball’’states, and states with quasirectangular or quasicircular symmetry. The above features are associated with nonisolated periodic orbits. Some states are observed which can be associated with isolated periodic orbits, leading to scars. This work represents the first direct experimental observation of scarred eigenfunctions. At high frequencies the eigenfunctions are very complex, and are yet to be classified in a general scheme.},
keywords = {Chemical & Biological Physics},
pubstate = {published},
tppubtype = {article}
}
Wei, Y-Z; Sridhar, S
Radiation-corrected open-ended coax line technique for dielectric measurements of liquids up to 20 GHz Journal Article
In: IEEE Transactions on Microwave Theory and Techniques, vol. 39, no. 3, pp. 526–531, 1991.
Abstract | BibTeX | Tags: Superconductivity
@article{wei1991radiation,
title = {Radiation-corrected open-ended coax line technique for dielectric measurements of liquids up to 20 GHz},
author = {Y-Z Wei and S Sridhar},
year = {1991},
date = {1991-01-01},
journal = {IEEE Transactions on Microwave Theory and Techniques},
volume = {39},
number = {3},
pages = {526--531},
publisher = {IEEE},
abstract = {An experimental technique and associated analysis are described for the measurement of the dielectric constants of liquids at microwave frequencies using an open-ended coax probe. The analysis includes radiative corrections to the probe-liquid interface impedance. The technique is applicable to liquid and liquid-like (e.g., biological) samples, having dielectric constants comparable to water, at frequencies up to 20 GHz and possibly as high as 40 GHz.<>},
keywords = {Superconductivity},
pubstate = {published},
tppubtype = {article}
}
Zahopoulos, C; Sridhar, S; Bautista, JJ; Ortiz, G; Lanagan, M
Performance of a high T c superconducting ultralow-loss microwave stripline filter Journal Article
In: Applied physics letters, vol. 58, no. 9, pp. 977–979, 1991.
BibTeX | Tags: Superconductivity
@article{zahopoulos1991performance,
title = {Performance of a high T c superconducting ultralow-loss microwave stripline filter},
author = {C Zahopoulos and S Sridhar and JJ Bautista and G Ortiz and M Lanagan},
year = {1991},
date = {1991-01-01},
journal = {Applied physics letters},
volume = {58},
number = {9},
pages = {977--979},
publisher = {American Institute of Physics},
keywords = {Superconductivity},
pubstate = {published},
tppubtype = {article}
}
Wu, Dong-Ho; Sridhar, S
Erratum:``Pinning forces and lowere critical fields in YBa2Cu3Oy crystals: Temperature dependence and anisotropy''[Phys. Rev. Lett. 65, 2074 (1990)] Journal Article
In: Physical Review Letters, vol. 66, pp. 968–968, 1991.
BibTeX | Tags: Superconductivity
@article{wu1991erratum,
title = {Erratum:``Pinning forces and lowere critical fields in YBa2Cu3Oy crystals: Temperature dependence and anisotropy''[Phys. Rev. Lett. 65, 2074 (1990)]},
author = {Dong-Ho Wu and S Sridhar},
year = {1991},
date = {1991-01-01},
journal = {Physical Review Letters},
volume = {66},
pages = {968--968},
keywords = {Superconductivity},
pubstate = {published},
tppubtype = {article}
}
Bautista, JJ; Ortiz, GERARDOG; Zahopoulos, C; Sridhar, S; Lanagan, M
Performance of a high T (sub c) superconducting ultra-low loss microwave stripline filter Journal Article
In: 1991.
Abstract | BibTeX | Tags: Superconductivity
@article{bautista1991performance,
title = {Performance of a high T (sub c) superconducting ultra-low loss microwave stripline filter},
author = {JJ Bautista and GERARDOG Ortiz and C Zahopoulos and S Sridhar and M Lanagan},
year = {1991},
date = {1991-01-01},
abstract = {Discussed here is the successful fabrication of a five-pole interdigital stripline filter made of the 93 K superconductor (Y1Ba2Cu3O sub y) coated on a silver substrate, with center frequency of 8.5 GHz and an extremely high rejection ratio of 80 dB. The lowest injection loss measured was 0.1 dB at 12 K, with a return loss of better than 16 dB, representing a significant improvement over a similar copper filter, and is comparable to low critical temperature filters. The insertion loss appears to be limited by extrinsic factors, such as tuning mismatch and joint losses, and not by superconducting material losses.},
keywords = {Superconductivity},
pubstate = {published},
tppubtype = {article}
}
Wu, Dong-Ho; Sridhar, S
Wu and Sridhar reply Journal Article
In: Physical review letters, vol. 67, no. 11, pp. 1474, 1991.
Abstract | BibTeX | Tags: Superconductivity
@article{wu1991wu,
title = {Wu and Sridhar reply},
author = {Dong-Ho Wu and S Sridhar},
year = {1991},
date = {1991-01-01},
journal = {Physical review letters},
volume = {67},
number = {11},
pages = {1474},
publisher = {APS},
abstract = {A reply to the comment on relation between Bc and pinning-force constant in YBaCuO is given. The authors claim they did not say Bc is anisotropic, and though Bc is isotropic, pinning-force constant need not be. The relation between these two arises under assumptions of core pinning.(AIP)},
keywords = {Superconductivity},
pubstate = {published},
tppubtype = {article}
}
1990
Wu, Dong-Ho; Sridhar, S
Pinning forces and lower critical fields in YBa 2 Cu 3 O y crystals: Temperature dependence and anisotropy Journal Article
In: Physical review letters, vol. 65, no. 16, pp. 2074, 1990.
Abstract | BibTeX | Tags: Superconductivity
@article{wu1990pinning,
title = {Pinning forces and lower critical fields in YBa 2 Cu 3 O y crystals: Temperature dependence and anisotropy},
author = {Dong-Ho Wu and S Sridhar},
year = {1990},
date = {1990-01-01},
journal = {Physical review letters},
volume = {65},
number = {16},
pages = {2074},
publisher = {APS},
abstract = {Measurements of the field-dependent radiofrequency penetration depth λ (H, T) are used to delineate the lower-critical-field H c 1-T phase boundary, and to study flux dynamics in YBa 2 Cu 3 O y crystals. For both H∥ c^ and H⊥ c^ H c 1 obeys a BCS temperature dependence with a temperature-independent anisotropy of 3.4±0.3. In the mixed state, the data obey λ 2 (H)=[φ 0/μ 0 α (T)] B (H), and yield both the functional dependence B (H) and the pinning force constant α (T). The latter is anisotropic, obeys an approximately (1-t 2) 2 temperature dependence, and vanishes slightly below the bulk transition temperature.},
keywords = {Superconductivity},
pubstate = {published},
tppubtype = {article}
}
Wei, Yan-Zhen; Sridhar, S
Dielectric spectroscopy up to 20 GHz of LiCl/H2O solutions Journal Article
In: The Journal of chemical physics, vol. 92, no. 2, pp. 923–928, 1990.
Abstract | BibTeX | Tags: Chemical & Biological Physics
@article{wei1990dielectric,
title = {Dielectric spectroscopy up to 20 GHz of LiCl/H2O solutions},
author = {Yan-Zhen Wei and S Sridhar},
year = {1990},
date = {1990-01-01},
journal = {The Journal of chemical physics},
volume = {92},
number = {2},
pages = {923--928},
publisher = {American Institute of Physics},
abstract = {Detailed measurements of the complex dielectric function ε=ε’−iε‘ as functions of frequency between 45 MHz and 20 GHz and concentration c are presented and analyzed for LiCl/H2O solutions. In this frequency range, the dielectric response is due to free water molecules and the response of the bound water occurs at lower frequencies and is not observed. From the data, several parameters—the static and high frequency limiting values ε0 and ε∞, the dc conductivity σdc, the dielectric relaxation time τd, and the hydration number nhyd—are extracted. The dissociation is observed to be incomplete suggesting the presence of undissociated ion pairs. A dissociation parameter is inferred from the σdc data. A model which views the liquid as composed of free water, hydrated single ions, and hydrated ion pairs is used to analyze the ε0 data. With inclusion of the dissociation parameter, the model describes the data reasonably well for c≤5.1 M. At higher concentrations, a unique relaxation time is not observed indicating glasslike behavior.},
keywords = {Chemical & Biological Physics},
pubstate = {published},
tppubtype = {article}
}
Sridhar, S
Electrodynamics of Superconducting Y 1 Ba 2 Cu 3 O y Book Section
In: Superconductivity and Applications, pp. 207–215, Springer, Boston, MA, 1990.
BibTeX | Tags: Superconductivity
@incollection{sridhar1990electrodynamics,
title = {Electrodynamics of Superconducting Y 1 Ba 2 Cu 3 O y},
author = {S Sridhar},
year = {1990},
date = {1990-01-01},
booktitle = {Superconductivity and Applications},
pages = {207--215},
publisher = {Springer, Boston, MA},
keywords = {Superconductivity},
pubstate = {published},
tppubtype = {incollection}
}
1989
Sridhar, S
ELECTRODYNAMICS OF SUPERCONDUCTING YjBajCuaO Journal Article
In: Superconductivity and Applications, pp. 207, 1989.
Abstract | BibTeX | Tags: Superconductivity
@article{sridhar1989electrodynamics,
title = {ELECTRODYNAMICS OF SUPERCONDUCTING YjBajCuaO},
author = {S Sridhar},
year = {1989},
date = {1989-01-01},
journal = {Superconductivity and Applications},
pages = {207},
publisher = {Plenum Publishing Corporation},
abstract = {The response of superconductors to time-varying electromagnetic fields can yield detailed information on the nature of the superconducting state1. Experiments carried out at frequencies in the rf to mm-wave spectral region directly probe the collective response of the condensed electrons and of the quasiparticles, and in conventional superconductors, have been important in determining the gap, the density of states and confirming the nature of the pairing.
The basic parameter that is measured at these frequencies is the complex surface impedance Zs= R «+ i Xs. The surface resistance Rt is a measure of the power absorbed, while the surface reactance, which is proportional to the penetration depth A, is a measure of the reactive power exchanged between the field and the superconductors. These quantities can be computed, from the fundamental constitutive relation which relates current and vector potential for the supercoaductor, J=-QA, along with Maxwell's equation and suitable boundary conditions. Experiments can then be compared with detailed predictions for the kernel Q from microscopic theories.},
keywords = {Superconductivity},
pubstate = {published},
tppubtype = {article}
}
The basic parameter that is measured at these frequencies is the complex surface impedance Zs= R «+ i Xs. The surface resistance Rt is a measure of the power absorbed, while the surface reactance, which is proportional to the penetration depth A, is a measure of the reactive power exchanged between the field and the superconductors. These quantities can be computed, from the fundamental constitutive relation which relates current and vector potential for the supercoaductor, J=-QA, along with Maxwell's equation and suitable boundary conditions. Experiments can then be compared with detailed predictions for the kernel Q from microscopic theories.
Sridhar, S; Wu, Dong-Ho; Kennedy, W
Temperature dependence of electrodynamic properties of YBa 2 Cu 3 O y crystals Journal Article
In: Physical review letters, vol. 63, no. 17, pp. 1873, 1989.
Abstract | BibTeX | Tags: Superconductivity
@article{sridhar1989temperature,
title = {Temperature dependence of electrodynamic properties of YBa 2 Cu 3 O y crystals},
author = {S Sridhar and Dong-Ho Wu and W Kennedy},
year = {1989},
date = {1989-01-01},
journal = {Physical review letters},
volume = {63},
number = {17},
pages = {1873},
publisher = {APS},
abstract = {The temperature dependences of the radio-frequency penetration depth λ ab, microwave surface resistance R s, and the lower critical field H c 1 were measured for YBa 2 Cu 3 O y crystals. Pair-breaking effects of magnetic fields on λ ab, represented by a parameter k== d λ ab/d (H 2), were also measured. The temperature dependences of all these parameters λ ab, H c 1, k, and R s are in good agreement with the Bardeen-Cooper-Schrieffer temperature dependences for an s-wave superconductor, and suggest a mean-field behavior of the gap parameter.},
keywords = {Superconductivity},
pubstate = {published},
tppubtype = {article}
}
Wei, Yan-Zhen; Sridhar, S
Technique for measuring the frequency-dependent complex dielectric constants of liquids up to 20 GHz Journal Article
In: Review of scientific instruments, vol. 60, no. 9, pp. 3041–3046, 1989.
BibTeX | Tags: Chemical & Biological Physics
@article{wei1989technique,
title = {Technique for measuring the frequency-dependent complex dielectric constants of liquids up to 20 GHz},
author = {Yan-Zhen Wei and S Sridhar},
year = {1989},
date = {1989-01-01},
journal = {Review of scientific instruments},
volume = {60},
number = {9},
pages = {3041--3046},
publisher = {American Institute of Physics},
keywords = {Chemical & Biological Physics},
pubstate = {published},
tppubtype = {article}
}
Wu, Dong-Ho; Kennedy, WL; Zahopoulos, C; Sridhar, S
Characteristics and growth of single crystals of Y1Ba2Cu3O7 with superior microwave properties Journal Article
In: Applied physics letters, vol. 55, no. 7, pp. 696–698, 1989.
Abstract | BibTeX | Tags: Superconductivity
@article{wu1989characteristics,
title = {Characteristics and growth of single crystals of Y1Ba2Cu3O7 with superior microwave properties},
author = {Dong-Ho Wu and WL Kennedy and C Zahopoulos and S Sridhar},
year = {1989},
date = {1989-01-01},
journal = {Applied physics letters},
volume = {55},
number = {7},
pages = {696--698},
publisher = {American Institute of Physics},
abstract = {We report the fabrication and high‐frequency characterization of single crystals of Y1Ba2Cu3O7 with extremely sharp microwave transitions. The 10 GHz surface resistance Rs is less than 400 μΩ, at temperatures 4 K below the transition temperature. The electrodynamic characteristics of these crystals were examined via several measurements, and we demonstrate that high quality crystals which show very low Rs also possess small penetration depths λ(0)=1600 Å and small magnetic field effects on the penetration depth characterized by k(0)≡(dλ/dB2)T→0=10−3 Å/G2. In polycrystals, and even in poor single crystals, the presence of Josephson junctions of typical effective area ∼4 μm2 leads to poor microwave properties, with electrodynamic parameters orders of magnitude larger.},
keywords = {Superconductivity},
pubstate = {published},
tppubtype = {article}
}
Sridhar, S
Electrodynamics of superconducting Y sub 1 Ba sub 2 Cu sub 3 O sub y Journal Article
In: Superconductivity and Applications, pp. 207–15, 1989.
Abstract | BibTeX | Tags: Superconductivity
@article{sridhar1989electrodynamicsb,
title = {Electrodynamics of superconducting Y sub 1 Ba sub 2 Cu sub 3 O sub y},
author = {S Sridhar},
year = {1989},
date = {1989-01-01},
journal = {Superconductivity and Applications},
pages = {207--15},
abstract = {Discussion includes measurements of surface resistance and penetration depth carried out at rf and microwave frequencies on title crystals. (meeting proceedings).},
keywords = {Superconductivity},
pubstate = {published},
tppubtype = {article}
}
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}
}
1988
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}
}
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}
}
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}
}
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}
}
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}
}
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}
}
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}
}
Sridhar, S; Taborek, P
High-frequency structural relaxation in supercooled liquids Journal Article
In: The Journal of chemical physics, vol. 88, no. 2, pp. 1170–1176, 1988.
BibTeX | Tags: Chemical & Biological Physics
@article{sridhar1988high,
title = {High-frequency structural relaxation in supercooled liquids},
author = {S Sridhar and P Taborek},
year = {1988},
date = {1988-01-01},
journal = {The Journal of chemical physics},
volume = {88},
number = {2},
pages = {1170--1176},
publisher = {American Institute of Physics},
keywords = {Chemical & Biological Physics},
pubstate = {published},
tppubtype = {article}
}
SRIDHAR, SPP; KUMAR, R
Hemato-biochemical changes in calves during neonatal life Journal Article
In: Indian Journal Animal Health, pp. 105–109, 1988.
BibTeX | Tags: Chemical & Biological Physics
@article{sridhar1988hemato,
title = {Hemato-biochemical changes in calves during neonatal life},
author = {SPP SRIDHAR and R KUMAR},
year = {1988},
date = {1988-01-01},
journal = {Indian Journal Animal Health},
pages = {105--109},
keywords = {Chemical & Biological Physics},
pubstate = {published},
tppubtype = {article}
}
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}
}
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}
}
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}
}
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}
}
1987
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}
}
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}
}
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}
}
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}
}
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}
}
1986
Reagor, D; Sridhar, S; Gruner, G
Inertial dynamics of pinned charge-density-wave condensates. I. NbSe 3 Journal Article
In: Physical Review B, vol. 34, no. 4, pp. 2212, 1986.
Abstract | BibTeX | Tags: Collective Excitations
@article{reagor1986inertial,
title = {Inertial dynamics of pinned charge-density-wave condensates. I. NbSe 3},
author = {D Reagor and S Sridhar and G Gruner},
year = {1986},
date = {1986-01-01},
journal = {Physical Review B},
volume = {34},
number = {4},
pages = {2212},
publisher = {APS},
abstract = {Conductivity measurements are reported for the linear-chain compound
NbSe
3
in the frequency range 9–100 GHz. In both charge-density-wave (CDW) states, which develop at
T
1
=144 K and at
T
2
=59 K, a strongly frequency-dependent response is observed with Reσ(ω) decreasing with increasing frequency. The behavior is described in terms of a harmonic oscillator response, and in the measured spectral range the expression Re
σ
CDW
(ω)=(
ne
2
τ/
m
*
)[1 /(1+
ω
2
τ
2
)] provides an excellent account of our findings. We evaluate the effective mass
m
*
and damping constant τ from a fit to the above equation. The measured effective mass is only weakly temperature dependent, and in both CDW states is in good qualitative agreement with those determined using the theory of Lee, Rice, and Anderson. We also discuss the temperature-dependent damping constant, and a comparison with data taken in the radio-frequency range is given.
Received 28 October 1985
DOI:https://doi.org/10.1103/PhysRevB.34.2212
©1986 American Physical Society},
keywords = {Collective Excitations},
pubstate = {published},
tppubtype = {article}
}
NbSe
3
in the frequency range 9–100 GHz. In both charge-density-wave (CDW) states, which develop at
T
1
=144 K and at
T
2
=59 K, a strongly frequency-dependent response is observed with Reσ(ω) decreasing with increasing frequency. The behavior is described in terms of a harmonic oscillator response, and in the measured spectral range the expression Re
σ
CDW
(ω)=(
ne
2
τ/
m
*
)[1 /(1+
ω
2
τ
2
)] provides an excellent account of our findings. We evaluate the effective mass
m
*
and damping constant τ from a fit to the above equation. The measured effective mass is only weakly temperature dependent, and in both CDW states is in good qualitative agreement with those determined using the theory of Lee, Rice, and Anderson. We also discuss the temperature-dependent damping constant, and a comparison with data taken in the radio-frequency range is given.
Received 28 October 1985
DOI:https://doi.org/10.1103/PhysRevB.34.2212
©1986 American Physical Society
Sridhar, S; Reagor, D; Gruner, G
Inertial dynamics of pinned charge-density-wave condensates. II. Orthorhombic TaS 3 Journal Article
In: Physical Review B, vol. 34, no. 4, pp. 2223, 1986.
Abstract | BibTeX | Tags: Collective Excitations
@article{sridhar1986inertial,
title = {Inertial dynamics of pinned charge-density-wave condensates. II. Orthorhombic TaS 3},
author = {S Sridhar and D Reagor and G Gruner},
year = {1986},
date = {1986-01-01},
journal = {Physical Review B},
volume = {34},
number = {4},
pages = {2223},
publisher = {APS},
abstract = {Complex conductivity
σ
CDW
(
ω
,T) measurements in the ranges 10–110 GHz and 20–300 K are reported on the charge-density-wave (CDW) material orthorhombic
TaS
3
. In the CDW state between approximately 130 and 210 K, the complex conductivity obeys a Drude behavior
σ
CDW
(ω)=(
ne
2
τ/
m
*
)(1+i ωτ), which we associate with damped inertial response of the CDW. The measurements, together with earlier results in the radio-frequency spectral range, enable us to extract all the phenomenological parameters: damping constant τ, effective mass
m
*
, pinning frequency
ω
0
, and maximum CDW conductivity
σ
max
. The experimental results for these parameters are compared with available microscopic theories. The full dynamic response of the CDW between
10
7
and
10
11
Hz is also presented and shows the conductivity resonance well below the single-particle gap, representing both the relaxational and inertial dynamic response of the collective CDW mode. A comparison is made to similar results on the related CDW compound
NbSe
3
.
Received 28 October 1985
DOI:https://doi.org/10.1103/PhysRevB.34.2223
©1986 American Physical Society},
keywords = {Collective Excitations},
pubstate = {published},
tppubtype = {article}
}
σ
CDW
(
ω
,T) measurements in the ranges 10–110 GHz and 20–300 K are reported on the charge-density-wave (CDW) material orthorhombic
TaS
3
. In the CDW state between approximately 130 and 210 K, the complex conductivity obeys a Drude behavior
σ
CDW
(ω)=(
ne
2
τ/
m
*
)(1+i ωτ), which we associate with damped inertial response of the CDW. The measurements, together with earlier results in the radio-frequency spectral range, enable us to extract all the phenomenological parameters: damping constant τ, effective mass
m
*
, pinning frequency
ω
0
, and maximum CDW conductivity
σ
max
. The experimental results for these parameters are compared with available microscopic theories. The full dynamic response of the CDW between
10
7
and
10
11
Hz is also presented and shows the conductivity resonance well below the single-particle gap, representing both the relaxational and inertial dynamic response of the collective CDW mode. A comparison is made to similar results on the related CDW compound
NbSe
3
.
Received 28 October 1985
DOI:https://doi.org/10.1103/PhysRevB.34.2223
©1986 American Physical Society
Sridhar, S; Mercereau, JE
Nonequilibrium dynamics of quasiparticles in superconductors Journal Article
In: Physical Review B, vol. 34, no. 1, pp. 203, 1986.
Abstract | BibTeX | Tags: Collective Excitations
@article{sridhar1986nonequilibrium,
title = {Nonequilibrium dynamics of quasiparticles in superconductors},
author = {S Sridhar and JE Mercereau},
year = {1986},
date = {1986-01-01},
journal = {Physical Review B},
volume = {34},
number = {1},
pages = {203},
publisher = {APS},
abstract = {Small changes δ
R
s
in the 10-GHz surface resistance
R
s
of thin superconducting films of Sn and In, caused by an induced static current
J
0
have been measured. δ
R
s
was quadratic in
J
0
and both increases (δ
R
s
>0) and decreases (δ
R
s
<0) of absorption were observed. The increase is associated mainly with thermodynamic depression of the gap parameter due to the static current. On the other hand, the decrease of absorption, which implies an enhancement of superconductivity, is incompatible with thermodynamic analysis. A nonequilibrium analysis is presented, according to which the combined static and high-frequency currents cause a nonthermal, time-dependent oscillation of the quasiparticle distribution, and which is out of phase with the driving high-frequency field. The counter oscillation leads to an enhancement of high-frequency supercurrent and decrease of dissipative normal current, and hence results in a decrease of absorption. The analysis describes the experimental results for very thin films of Sn both qualitatively and quantitatively, and with no adjustable parameters. These results lead to the conclusion that at high frequencies, the superconductor responds to time-dependent perturbations in an inherently nonadiabatic, nonequilibrium manner even for vanishingly small high-frequency fields. The implications for several unexplained experiments on the magnetic field dependence of
R
s
are discussed.
Received 24 January 1986
DOI:https://doi.org/10.1103/PhysRevB.34.203
©1986 American Physical Society},
keywords = {Collective Excitations},
pubstate = {published},
tppubtype = {article}
}
R
s
in the 10-GHz surface resistance
R
s
of thin superconducting films of Sn and In, caused by an induced static current
J
0
have been measured. δ
R
s
was quadratic in
J
0
and both increases (δ
R
s
>0) and decreases (δ
R
s
<0) of absorption were observed. The increase is associated mainly with thermodynamic depression of the gap parameter due to the static current. On the other hand, the decrease of absorption, which implies an enhancement of superconductivity, is incompatible with thermodynamic analysis. A nonequilibrium analysis is presented, according to which the combined static and high-frequency currents cause a nonthermal, time-dependent oscillation of the quasiparticle distribution, and which is out of phase with the driving high-frequency field. The counter oscillation leads to an enhancement of high-frequency supercurrent and decrease of dissipative normal current, and hence results in a decrease of absorption. The analysis describes the experimental results for very thin films of Sn both qualitatively and quantitatively, and with no adjustable parameters. These results lead to the conclusion that at high frequencies, the superconductor responds to time-dependent perturbations in an inherently nonadiabatic, nonequilibrium manner even for vanishingly small high-frequency fields. The implications for several unexplained experiments on the magnetic field dependence of
R
s
are discussed.
Received 24 January 1986
DOI:https://doi.org/10.1103/PhysRevB.34.203
©1986 American Physical Society
1985
Sridhar, S; Reagor, D; Gruner, G
Inertial Dynamics of Charge-Density Waves in Ta S 3 and Nb Se 3 Journal Article
In: Physical review letters, vol. 55, no. 11, pp. 1196, 1985.
Abstract | BibTeX | Tags: Collective Excitations
@article{sridhar1985inertial,
title = {Inertial Dynamics of Charge-Density Waves in Ta S 3 and Nb Se 3},
author = {S Sridhar and D Reagor and G Gruner},
year = {1985},
date = {1985-01-01},
journal = {Physical review letters},
volume = {55},
number = {11},
pages = {1196},
publisher = {APS},
abstract = {Frequency-dependent complex-conductivity measurements are reported in the charge-density-wave states of Ta S 3 and Nb Se 3, in the 10—100-GHz spectral region. A Drude-type behavior associated with damped inertial response of the condensate is observed for the first time. The fundamental parameters that characterize the dynamics of the collective mode (damping constant, pinning energy, and effective mass) are obtained. The results for the effective mass and damping are compared with microscopic theories.},
keywords = {Collective Excitations},
pubstate = {published},
tppubtype = {article}
}
Reagor, D; Sridhar, S; Maki, M; Gruner, G
Inertial charge-density-wave dynamics in (TaSe 4) 2 I Journal Article
In: Physical Review B, vol. 32, no. 12, pp. 8445, 1985.
Abstract | BibTeX | Tags: Collective Excitations
@article{reagor1985inertial,
title = {Inertial charge-density-wave dynamics in (TaSe 4) 2 I},
author = {D Reagor and S Sridhar and M Maki and G Gruner},
year = {1985},
date = {1985-01-01},
journal = {Physical Review B},
volume = {32},
number = {12},
pages = {8445},
publisher = {APS},
abstract = {Frequency-dependent conductivity measurements are reported in the charge-density-wave (CDW) state of the linear-chain compound (TaSe 4) 2 I in the spectral range 4.5–94 GHz. In contrast to other CDW systems which are overdamped, the response is underdamped, with a resonant frequency of approximately 35 GHz, a resonance width of approximately 20 GHz, and an effective mass of 10 4. The large effective mass, large resonant frequency, and small damping are a consequence of the strong electron-phonon coupling in this system.},
keywords = {Collective Excitations},
pubstate = {published},
tppubtype = {article}
}