Spectroscopic and optical response of odd-frequency superconductors

TL;DR

This paper investigates the optical properties of odd-frequency superconductors, revealing unique spectral features and potential transparency windows that distinguish them from conventional BCS superconductors.

Contribution

It provides a theoretical analysis of the optical response of Berezinskii odd-frequency superconductors, highlighting distinctive spectral and conductivity signatures.

Findings

Odd-frequency gaps produce sharper peaks in conductivity than BCS gaps.

Spectral functions clearly reveal the superconducting gap for strong frequency dependence.

Optical transparency windows may exist due to attenuation peaks in the optical response.

Abstract

The optical response of superconductors with odd-frequency Berezinskii pairing is studied. By using a simple model with a parabolic dispersion law and a non-magnetic disorder, the spectral function, the electron density of states, and the optical conductivity are calculated for a few gap ansatzes. The spectral function and the electron density of states clearly reveal the gap for the Berezinskii pairing for the sufficiently strong frequency dependence of the order parameters. It is found that, similarly to the conventional BCS pairing, the odd-frequency gaps induce peaks in the real part of the conductivity, which, however, are sharper than in the BCS case. The magnitude and position of these peaks are determined by the frequency profile of the gap. The imaginary part of the optical conductivity for the Berezinskii pairing demonstrates sharp cusps that are absent in the case of the BCS superconductors. The corresponding results suggest that the Berezinskii pairing might allow for the optical transparency windows related to the onsets of the attenuation peaks in the real part of the conductivity. Thus, the study of the optical response not only provides an alternative way to probe the odd-frequency gaps but can reveal also additional features of the dynamic superconducting pairing.