Role of Symmetry in Raman Spectroscopy of Unconventional Superconductors

TL;DR

This paper explores how symmetry influences Raman spectra in unconventional superconductors, emphasizing the effects of doping, disorder, and spin fluctuations on the energy gap and spectral features.

Contribution

It provides a detailed theoretical analysis of symmetry effects on Raman spectra, especially in bi-layer cuprates, constraining the energy gap symmetry and magnitude.

Findings

The $B_{1g}$ channel is highly sensitive to doping effects.

A $d_{x^{2}-y^{2}}$ symmetry gap best fits the Raman data.

Disorder and spin fluctuations significantly influence spectral features.

Abstract

The role of symmetry of the inelastic light scattering amplitude, the superconducting energy gap, and the underlying Fermi surface manifold on the Raman spectra of unconventional superconductors is discussed in detail. Particular emphasis is placed on both single and bi-layer superconductors. It is found that the $B_{1g}$ channel may be the most sensitive to doping due to the role of the Van Hove singularity. Lastly the effects of both disorder and spin fluctuations are considered. The theory imposes strong constraints on both the magnitude and symmetry of the energy gap for the bi-layer cuprates, indicating that a nearly identical energy gap of $d_{x^{2}-y^{2}}$ symmetry provides a best fit to the data.