The high temperature superconductors which were discovered in 1986 still continue to pose major challenges to scientists. Not only is the mechanism for superconductivity not known, but the nature of the superconducting state and the motion of vortices continue to be debated intensely. We study the microwave response of superconductors, both for understanding the nature of superconductivity, the dynamics of vortices and for practical applications in microwave devices.

The principal areas of our research are:

  • Fundamental measurements and analysis of the penetration depth and surface impedance of superconductors, with a view to understanding the pairing state, the quasiparticle spectrum and the gap parameter
  • Vortex dynamics at high (rf and microwave) frequencies to obtain quantiative measurements of parameters such as pinning force constants, vortex viscosity, critical fields, melting and vortex glass transitions
  • Flux penetration and critical state dynamics
  • Josephson type nonlinear phenomena at microwave frequencies
  • Development of novel measurement techniques, such as the “hot finger” cavity method to measure surface impedance, tunnel diode technique of measuring penetration depth, patterned film structures to study vortex dynamics, modulated microwave absorption

The materials we study are the cuprate High Tc superconductors, borocarbides, and organic superconductors.

Our work in Superconductivity is supported by:

  • National Science Foundation
  • Division of Materials Research and Division of Electrical and Communications Systems, Rome Laboratory, Hanscom AFB (an AFOSR lab)

Related Publications

Choudhury, Durga P; Derov, John S; Sridhar, S
Harmonic generation from YBa2Cu3O7- $delta$ microwave resonators Journal Article

(Tags: Superconductivity)

Measurement, 2008.
Choudhury, Durga P; Sridhar, S
Superconducting microwave technology Journal Article

(Abstract | Tags: Superconductivity)

Encyclopedia of RF and Microwave Engineering, 2005.
Bishop, Alan R; Srinivas, Sridhar; others,
Intrinsic Multiscale Structure and Dynamics in Complex Electronic Oxides, Proceedings of the Workshop Miscellaneous

(Abstract | Tags: Superconductivity)

2003.
Sridhar, S; Shenoy, SR; for Physics, Abdus Salam International Centre Theoretical; Bishop, AR
Proceedings of the Workshop: Intrinsic Multiscale Structure and Dynamics in Complex Electronic Oxides (Intrinsic Multiscale Structure and Dynamics in Complex Electronic Oxides) Miscellaneous

(Tags: Superconductivity)

2003.
Sridhar, S; Kusko, C; Zhai, Z
Is There a Narrow Conductivity Mode in the Superconducting Oxides? Incollection

(Abstract | Tags: Superconductivity)

Intrinsic Multiscale Structure And Dynamics In Complex Electronic Oxides, pp. 69–83, 2003.
Hakim, Nazih; Kusko, Christian; Sridhar, Srinivas
Microwave and Radio Frequency Response of MgB_2. Inproceedings

(Abstract | Tags: Superconductivity)

APS Meeting Abstracts, 2003.
Hakim, Nazih; Parimi, Patanjali; Kusko, Christian; Sridhar, Srinivas
Microwave and Radio Frequency, RF, Measurements on Superconducting MgB_2. Inproceedings

(Abstract | Tags: Superconductivity)

APS Meeting Abstracts, 2002.
Kusko, C; Zhai, Z; Hakim, N; Markiewicz, RS; Sridhar, S; Colson, D; Viallet-Guillen, V; Forget, A; Nefyodov, Yu A; Trunin, MR; others,
Anomalous microwave conductivity due to collective transport in the pseudogap state of cuprate superconductors Journal Article

(Abstract | Tags: Superconductivity)

Physical Review B, 65 (13), pp. 132501, 2002.
Bishop, AR; Shenoy, SR; Sridhar, S
Intrinsic Multiscale Structure and Dynamics in Complex Electronic Oxides Inproceedings

(Abstract | Tags: Superconductivity)

World Scientific Singapore Proceedings of the Workshop ICTP, Trieste, Italy 2002.
Hakim, N; Kusko, C; Sridhar, S; Soukiassian, A; Zeng, XH; Xi, XX
The superconducting gap of in situ MgB 2 thin films by microwave surface impedance measurements Journal Article

(Tags: Superconductivity)

Applied Physics Letters, 81 (19), pp. 3603–3605, 2002.
Sridhar, S
Microwave Properties of Superconducting MgB_2 Inproceedings

(Tags: Superconductivity)

APS Meeting Abstracts, 2002.
Hakim, Nazih; Parimi, Patanjali V; Nyeanchi, Emmanuel; Sridhar, Srinivas; Chou, F-C
Microwave properties of superconducting and insulating La_2-xSr_xCuO_4 Inproceedings

(Abstract | Tags: Superconductivity)

APS Meeting Abstracts, 2001.
Kusko, C; Zhai, Z; Hakim, N; Sridhar, S
Signature of the pseudogap state in microwave transport in cuprate superconductors Inproceedings

(Abstract | Tags: Superconductivity)

APS Meeting Abstracts, 2001.
Zhai, Z; Kusko, C; Sridhar, S
Anomalous microwave scattering rate in cuprate superconductors Inproceedings

(Abstract | Tags: Superconductivity)

APS Meeting Abstracts, 2001.
Kusko, C; Zhai, Z; Markiewicz, RS; Sridhar, S
Anomalous scattering rate and microwave absorption in Bi₂Sr₂CaCu₂O₈₊ $delta$ and Y Ba₂Cu₃O₇₋ $delta$ Journal Article

(Tags: Superconductivity)

2001.
Parimi, Patanjali; Hakim, Nazih; Sridhar, Srinivas
Dielectric transitions driven by local lattice distortions in perovskite oxides, YBa2 Cu3 O_6. 0, La_2CuO4 and La_5/3Sr_1/3NiO_4. Inproceedings

(Abstract | Tags: Superconductivity)

APS March Meeting Abstracts, 2001.
Hakim, N; Parimi, PV; Kusko, C; Sridhar, S; Canfield, Paul C; Bud’ko, Sergey L; Finnemore, Douglas K
Microwave properties of superconducting MgB 2 Journal Article

(Tags: Superconductivity)

Applied Physics Letters, 78 (26), pp. 4160–4162, 2001.
Zhai, Z; Parimi, PV; Sokoloff, JB; Sridhar, S; Erb, A
Onset of dielectric modes at 110 K and 60 K due to local lattice distortions in nonsuperconducting YBa 2 Cu 3 O 6.0 crystals Journal Article

(Abstract | Tags: Superconductivity)

Physical Review B, 63 (9), pp. 092508, 2001.
Dasgupta, T; Derov, JS; Sridhar, S
Computer-aided modeling of superconducting striplines with ground planes using critical state models Journal Article

(Abstract | Tags: Superconductivity)

Journal of Applied Physics, 90 (6), pp. 2915–2918, 2001.
PARIMI, PV; SRIKANTH, H; BAILLEUL, M; SRIDHAR, S
R. SURYANARAYANAN, L. PINSARD and A. REVCOLEVSCHI. Journal Article

(Abstract | Tags: Superconductivity)

Tc, 200 (250), pp. 300, 2001.
Kusko, C; Zhai, Z; Markiewicz, RS; Sridhar, S
Anomalous Scattering Rate and Microwave Absorption in Bi2Sr2CaCu2O8+ $delta$ and YBa2Cu3O7- $delta$ Journal Article

(Tags: Superconductivity)

Journal of superconductivity, 14 (1), pp. 81–84, 2001.
Dresselhaus, MS; Oates, D; Sridhar, S
Studies of High-T sub c Superconducting Films for High-Power Microwave Applications Technical Report

(Abstract | Tags: Superconductivity)

DTIC Document 2001.
Parimi, PV; Hakim, N; Chou, FC; Cheong, SW; Sridhar, S
Dielectric signatures of lattice instabilities at 32K and 245K in $ La_ $$2-y$$ Sr_ $$y$$ MO_ $$4+ x$$ $(M= Cu, Ni) Cuprates and Nickelates Journal Article

(Tags: Superconductivity)

arXiv preprint cond-mat/0108342, 2001.
Parimi, Patanjali; Zhai, Zhiyong; Hakim, Nazih; Kusko, Christian; Sridhar, Srinivas; Amerahl, Udo; Vietkine, A; Revcolevschi, A
Charge Polarization Dynamics of Spin-Ladder and Spin-Chain Sr-Cu-O Cuprates. Inproceedings

(Abstract | Tags: Collective Excitations, Magnetism, Superconductivity)

APS Meeting Abstracts, 2000.
Xin, H; Oates, DE; Sridhar, S; Dresselhaus, G; Dresselhaus, MS
RAPID COMMUNICATIONS-Superfluidity and superconductivity-Observation of individual Josephson vortices in YBa2Cu3O7-d bicrystal grain-boundary junctions Journal Article

(Tags: Superconductivity)

Physical Review-Section B-Condensed Matter, 61 (22), pp. R14952, 2000.
Zhai, Z; Kusko, C; Hakim, N; Sridhar, S; Revcolevschi, A; Vietkine, A
Precision microwave dielectric and magnetic susceptibility measurements of correlated electronic materials using superconducting cavities Journal Article

(Abstract | Tags: Superconductivity)

Review of Scientific Instruments, 71 (8), pp. 3151–3160, 2000.
Xin, Hao; Oates, DE; Sridhar, S; Dresselhaus, G; Dresselhaus, MS
Observation of individual Josephson vortices in YBa 2 Cu 3 O 7- $delta$ bicrystal grain-boundary junctions Journal Article

(Tags: Superconductivity)

Physical Review B, 61 (22), pp. R14952, 2000.
Zhai, Z; Parimi, Patanjali V; Sridhar, S
Erratum: Nonlinear microwave impedance of short and long Josephson junctions [Phys. Rev. B 59, 9573 (1999)] Journal Article

(Abstract | Tags: Superconductivity)

Physical Review B, 62 (17), pp. 11888, 2000.
Sridhar, S; Giannakopoulos, AE; Suresh, S
STRUCTURAL, MECHANICAL, THERMODYNAMIC, AND OPTICAL PROPERTIES OF CONDENSED MATTER (PACS 61-68, 78)-Mechanical and electrical responses of piezoelectric solids to conical indentation Journal Article

(Tags: Superconductivity)

Journal of Applied Physics, 87 (12), pp. 8451–8456, 2000.
Sridhar, S; Zhai, Z
Non-quasiparticle microwave absorption in Bi2Sr2CaCu2O8+ $delta$ Journal Article

(Tags: Superconductivity)

Physica C: Superconductivity, 341 , pp. 2057–2060, 2000.
Parimi, PV; Srikanth, H; Bailleul, M; Sridhar, S; Suryanarayanan, R; Pinsard, L; Revcolevschi, A
rf Susceptibility of La 1- x Sr x MnO 3 Single Crystals: Magnetic Signatures of Structural Changes Journal Article

(Tags: Magnetism, Superconductivity)

MRS Online Proceedings Library Archive, 602 , 1999.
Dasgupta, T; Choudhury, Durga P; Sridhar, S
Modeling nonlinearity and hysteresis due to critical-state flux penetration in hard superconductors Journal Article

(Abstract | Tags: Superconductivity)

arXiv preprint cond-mat/9905063, 1999.
Patanjali, PV; Theule, P; Zhai, Z; Hakim, N; Sridhar, S; Suryanarayanan, R; Apostu, M; Dhalenne, G; Revcolevschi, A
High-frequency magnetoimpedance of double perovskite La 1.2 Sr 1.8 Mn 2 O 7: Secondary transitions at high temperatures Journal Article

(Abstract | Tags: Magnetism, Superconductivity)

Physical Review B, 60 (13), pp. 9268, 1999.
Zhai, Z; Patanjali, PV; Hakim, N; Sokoloff, JB; Sridhar, S; Ammerahl, U; Vietkine, A; Revcolevschi, A
Observation of spin freezing and relaxation at microwave frequencies in the spin ladder compound $ Sr_ $$14-x$$ Ca_ $$x$$ Cu_ $$24$$ O_ $$41$$ $ Journal Article

(Tags: Superconductivity)

arXiv preprint cond-mat/9903198, 1999.
Sridhar, S; Zhai, Z; Erb, A
Microwave Absorption Peaks: Signatures of Spin Dynamics in Cuprates Journal Article

(Abstract | Tags: Superconductivity)

arXiv preprint cond-mat/9906053, 1999.
Choudhury, Durga P; Derov, John S; Sridhar, S
Harmonic generation from YBCO microwave resonators Journal Article

(Abstract | Tags: Superconductivity)

arXiv preprint cond-mat/9904080, 1999.
Zhai, Z; Parimi, Patanjali V; Sridhar, S
Nonlinear microwave impedance of short and long Josephson junctions Journal Article

(Tags: Superconductivity)

Physical Review B, 59 (14), pp. 9573, 1999.
Kidambi, V; Zhai, Z; Srikanth, H; Sridhar, S; Erb, A; Li, Qiang
Vortex response of YBCO and BSCCO single crystals from RF experiments Inproceedings

(Abstract | Tags: Superconductivity)

APS March Meeting Abstracts, 1998.
Srikanth, H; Revcolevschi, B; Choudhury, DP; Sridhar, S; Pinsard, L; Revcolevschi, A
High frequency electrodynamics of La_1-xSr_xMnO3 single crystals Inproceedings

(Abstract | Tags: Magnetism, Superconductivity)

APS March Meeting Abstracts, 1998.
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

(Abstract | Tags: Superconductivity)

Physical Review B, 57 (13), pp. 7986, 1998.
Zhai, Z; Srikanth, H; Sridhar, S; Erb, A
Microwave properties of YBCO and other cuprate single crystals Inproceedings

(Abstract | Tags: Superconductivity)

APS March Meeting Abstracts, 1998.
Bansil, A; Markiewicz, B; Sridhar, S; Liebenberg, D
Spectroscopies in novel superconductors-Preface Miscellaneous

(Tags: Superconductivity)

1998.
Srikanth, H; Zhai, Z; Sridhar, S; Erb, A
Microwave properties of YBCO crystals grown in BaZrO3 crucibles: influence of c-axis currents Journal Article

(Abstract | Tags: Superconductivity)

Journal of Physics and Chemistry of Solids, 59 (10-12), pp. 2105–2109, 1998.
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

(Abstract | Tags: Superconductivity)

Physical Review B, 58 (21), pp. 14490, 1998.
Choudhury, Durga P; Derov, John S; Sridhar, S
Measurement and modeling of nonlinear microwave response of high temperature superconductors Inproceedings

(Abstract | Tags: Magnetism, Superconductivity)

APS March Meeting Abstracts, 1998.
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

(Abstract | Tags: Superconductivity)

arXiv preprint cond-mat/9610032, 1997.
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

(Tags: Superconductivity)

Physical review letters, 78 (10), pp. 1968, 1997.
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

(Abstract | Tags: Superconductivity)

Physical Review B, 55 (22), pp. R14733, 1997.
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 Inproceedings

(Abstract | Tags: Superconductivity)

APS March Meeting Abstracts, 1997.
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

(Abstract | Tags: Superconductivity)

IEEE transactions on applied superconductivity, 7 (2), pp. 1260–1263, 1997.