Cooper-pair-condensate fluctuations and plasmons in layered superconductors
- Departement de Physique, Centre de Recherche en Physique du Solide, Universite de Sherbrooke, Sherbrooke, Quebec, J1K2R1 (Canada)
- Department of Physics, University of Toronto, Toronto, Ontario, M5S1A7 (Canada)
Starting from a given attractive potential, we give a systematic analysis of the spin-singlet [ital s]-wave Cooper-pair-condensate fluctuations in a two-dimensional (2D) superconductor. These results are applied to a superlattice of superconducting sheets in which the 2D charge fluctuations are coupled via the Coulomb interaction. Our main interest is how the low-energy Anderson-Bogoliubov (AB) phonon mode in the pair-breaking gap [omega][lt]2[Delta] is modified by the Coulomb interaction. Our formal analysis is valid at arbitrary temperatures. It describes the weakly bound, large-Cooper-pair limit as well as the strongly bound, small-Cooper-pair limit and thus includes both the BCS and Bose-Einstein scenarios (as discussed by Nozieres and Schmitt-Rink as well as Randeira [ital et] [ital al].). A comlete normal-mode analysis is given for a charged BCS superconductor, showing how the repulsive (Coulomb) interaction modifies the collective modes of a neutral superconductor. This complements the recent numerical study carried out by Fertig and Das Sarma. We show that the pair-response function shares the same spectrum as the charge-response function, given by the zero of the longitudinal dielectric function [epsilon]([bold q],[omega]). In 2D and layered superconductors, there is a low-frequency and high-frequency plasmon branch, separated by a relatively narrow particle-hole continuum at around 2[Delta]. The low-frequency ([omega][lt]2[Delta]) plasmon branch is a renormalized version of the AB phonon mode.
- OSTI ID:
- 5945483
- Journal Information:
- Physical Review, B: Condensed Matter; (United States), Vol. 48:14; ISSN 0163-1829
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
SUPERCONDUCTIVITY AND SUPERFLUIDITY
SUPERCONDUCTORS
PLASMONS
BCS THEORY
BOSE-EINSTEIN CONDENSATION
COOPER PAIRS
FLUCTUATIONS
S STATES
TWO-DIMENSIONAL CALCULATIONS
ENERGY LEVELS
QUASI PARTICLES
VARIATIONS
665411* - Basic Superconductivity Studies- (1992-)
665200 - Solid-State Plasma- (1992-)