Screening in (d+s)-wave superconductors: Application to Raman scattering

Abstract

We study the polarization-dependent electronic Raman response of untwinned YBa${}_2$Cu${}_3$O${}_{7-\delta }$ superconductors employing a tight-binding band structure with anisotropic hopping matrix parameters and a superconducting gap with a mixing of $d$- and s-wave symmetry. Using general arguments we find screening terms in the $B^{\}_{1g}$ scattering channel which are required by gauge invariance. As a result, we obtain a small but measurable softening of the pair-breaking peak, whose position has been attributed for a long time to twice the superconducting gap maximum. Furthermore, we predict superconductivity-induced changes in the phonon line shapes that could provide a way to detect the isotropic s-wave admixture to the superconducting gap.

typos corrected, 6 pages, 3 figures

References in corpus (1)

• Inelastic Light Scattering From Correlated Electrons