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

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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

In: APS Meeting Abstracts, 2000.

Abstract | Tags: Collective Excitations, Magnetism, Superconductivity

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 | Tags: Collective Excitations

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 | Tags: Collective Excitations

Sridhar, S; Mercereau, JE

Nonequilibrium dynamics of quasiparticles in superconductors Journal Article

In: Physical Review B, vol. 34, no. 1, pp. 203, 1986.

Abstract | Tags: Collective Excitations

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 | Tags: Collective Excitations

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 | Tags: Collective Excitations

Javadi, HHS; Sridhar, S; Grüner, G; Chiang, Long; Wudl, F

Giant conductivity resonance in the spin-density-wave state of an organic conductor Journal Article

In: Physical review letters, vol. 55, no. 11, pp. 1216, 1985.

Abstract | Tags: Collective Excitations

Sridhar, S; Reagor, D; Gruner, G

Complex conductivity measurements between 26 and 110 GHz using complex impedance bridges Journal Article

In: Review of scientific instruments, vol. 56, no. 10, pp. 1946–1952, 1985.

Abstract | Tags: Collective Excitations

Reagor, D; Sridhar, S; Grüner, G

Inertial dynamics of CDW transport in NbSe 3 Incollection

In: Charge Density Waves in Solids, pp. 308–310, Springer, Berlin, Heidelberg, 1985.

Tags: Collective Excitations

JAVADI, HHS; SRIDHAR, S; GRUNER, G; NALEVAJEK, L; COX, S; WUDL, F

SPIN-DENSITY WAVE RESPONSE IN (TMTSF) 2PF6 AND ITS ALLOYS Inproceedings

In: MOLECULAR CRYSTALS AND LIQUID CRYSTALS, pp. 390–390, GORDON BREACH SCI PUBL LTD C/O STBS LTD, PO BOX 90, READING, BERKS, ENGLAND~… 1985.

Tags: Collective Excitations

REAGOR, D; SRIDHAR, S; GRUNER, G

THE HIGH-FREQUENCY LIMIT OF CHARGE-DENSITY CONDUCTION Inproceedings

In: MOLECULAR CRYSTALS AND LIQUID CRYSTALS, pp. 414–414, GORDON BREACH SCI PUBL LTD C/O STBS LTD, PO BOX 90, READING, BERKS, ENGLAND~… 1985.

Tags: Collective Excitations