Paper
Plasmon excitations and their attenuation in dirty superconductors
Authors
Daniil K. Karuzin, Mikhail A. Skvortsov
Abstract
We develop a theory for the plasmon spectrum in dirty superconductors across the entire temperature range. Starting with the microscopic Keldysh sigma model description, we link the plasmon dispersion to the optical conductivity of a superconductor, which requires analytical continuation to the lower half-plane of complex frequency. This approach reveals a discontinuity at the superconducting transition: a jump in both the real and imaginary parts of at . For any temperature below , the plasmon dispersion terminates at a critical wave vector where plasmons remains undamped, with weakly -dependent . Plasmons significantly attenuate only within a narrow 5% temperature window near , with the propagating mode recovering at large .