Proposal for Plasmon Spectroscopy of Fluctuations in Low-Dimensional Superconductors

TL;DR

This paper proposes a novel optical spectroscopy method to detect superconducting fluctuations in low-dimensional superconductors near the critical temperature, revealing plasmon shifts and fluctuation-induced current corrections.

Contribution

It introduces a new spectroscopic approach to monitor superconducting fluctuations via plasmon resonance effects in two-dimensional systems.

Findings

Fluctuating Cooper pairs cause a redshift in plasmon dispersion.

Superconducting fluctuations induce measurable corrections to electric currents.

A drag effect of fluctuations results in observable current modifications near plasmon resonance.

Abstract

We propose to employ an optical spectroscopy technique to monitor the superconductivity and properties of superconductors in the fluctuating regime. This technique is operational close to the plasmon resonance frequency of the material, and it intimately connects with the superconducting fluctuations slightly above the critical temperature $T_c$. We find the Aslamazov-Larkin corrections to AC linear and DC nonlinear electric currents in a generic two-dimensional system exposed to an external longitudinal electromagnetic field. First, we study the plasmon resonance of normal electrons near $T_c$, taking into account their interaction with superconducting fluctuations, and show that fluctuating Cooper pairs reveal a redshift of the plasmon dispersion and an additional mechanism of plasmon scattering, which surpasses both the electron-impurity and the Landau dampings. Second, we demonstrate the emergence of a drag effect of superconducting fluctuations by the external field resulting in considerable, experimentally measurable corrections to the electric current in the vicinity of the plasmon resonance.