Electronic Raman scattering in YBCO and other superconducting cuprates

TL;DR

This paper computes electronic Raman spectra of high-Tc cuprates using ab initio band structure calculations, comparing results with experiments and analyzing the effects of Fermi surface and van Hove singularities.

Contribution

It provides a detailed theoretical analysis of Raman spectra in high-Tc superconductors based on first-principles calculations, including polarization effects and gap symmetry considerations.

Findings

Calculated spectra match experimental features with a d_(x^2-y^2) gap.

Fermi surface and van Hove singularities influence spectral structures.

Discrepancies exist in explaining A1g and B1g peak positions.

Abstract

Superconductivity induced structures in the electronic Raman spectra of high-Tc superconductors are computed using the results of ab initio LDA-LMTO three-dimensional band structure calculations via numerical integrations of the mass fluctuations, either in the whole 3D Brillouin zone or limiting the integrations to the Fermi surface. The results of both calculations are rather similar, the Brillouin zone integration yielding additional weak structures related to the extended van Hove singularities. Similar calculations have been performed for the normal state of these high-Tc cuprates. Polarization configurations have been investigated and the results have been compared to experimental spectra. The assumption of a simple d_(x^2-y^2)-like gap function allows us to explain a number of experimental features but is hard to reconcile with the relative positions of the A1g and B1g peaks.