Probing the pairing interaction and multiple Bardasis-Schrieffer modes using Raman spectroscopy

TL;DR

This paper develops a general theory for multiband Raman response in unconventional superconductors, identifying multiple Bardasis-Schrieffer modes that reveal the nature of pairing interactions and subleading gap structures.

Contribution

It introduces a comprehensive framework to interpret Raman spectra, linking collective modes to pairing interactions and subleading channels in multiband superconductors.

Findings

Identification of multiple Bardasis-Schrieffer modes in Raman spectra.

Connection of mode weights to subleading gap structures.

Application to interpret B1g Raman scattering in BaFe2As2.

Abstract

In unconventional superconductors, understanding the form of the pairing interaction is the primary goal. In this regard, Raman spectroscopy is a very useful tool, as it identifies the ground state and also the subleading pairing channels by probing collective modes. Here we propose a general theory for multiband Raman response and identify new features in the spectrum that can provide a robust test for a pairing theory. We identify multiple Bardasis-Schrieffer type collective modes and connect the weights of these modes to the sub-leading gap structures within a microscopic pairing theory. The conclusions are completely general, and we apply our approach to interpret the B1g Raman scattering in hole-doped BaFe2As2.