Coherent photogalvanic effect in fluctuating superconductors

TL;DR

This paper develops a theoretical framework for the coherent photogalvanic effect in fluctuating low-dimensional superconductors, revealing how electromagnetic fields induce a Cooper pair current sensitive to temperature and polarization.

Contribution

It introduces a novel theory describing the CPGE in fluctuating superconductors, including formulas for current density and polarization effects near the critical temperature.

Findings

Current exhibits non-monotonous spectrum at specific polarization angles.

Peak in the spectrum narrows and redshifts near the critical temperature.

Peak intensity increases significantly as temperature approaches critical point.

Abstract

We develop a theory of the coherent photogalvanic effect (CPGE) in low-dimensional superconductors in the fluctuating regime. It manifests itself in the appearance of a stationary electric current of Cooper pairs under the action of two coherent electromagnetic fields of light with frequencies lying in the sub-terahertz range. We derive the general formula for the electric current density, study the particular cases of linear and circular polarizations of the external light fields, and show that the current might have a non-monotonous spectrum at certain polarization angles and turns out very sensitive to the proximity of the ambient temperature to the critical temperature of superconducting transition: Approaching the critical temperature, the peak in the spectrum becomes narrower, its frequency experiences a redshift, and the intensity of the peak drastically grows.