Van Hove Singularity and D-Wave Pairing in Disordered Superconductors

TL;DR

This paper investigates how disorder affects the Van Hove singularity's role in enhancing the superconducting transition temperature in disordered d-wave superconductors, using CPA and comparing with experimental data.

Contribution

It provides a qualitative analysis of disorder effects on T_c and the Van Hove singularity in d-wave superconductors, supported by experimental comparisons.

Findings

Disorder reduces but does not eliminate the Van Hove singularity's enhancement of T_c.

The T_c vs. doping curve changes qualitatively with increasing disorder.

Results align qualitatively with experiments on specific cuprate alloys.

Abstract

We apply the coherent potential approximation (CPA) to a simple model for disordered superconductors with d-wave pairing. We demonstrate that whilst the effectiveness of an electronic Van Hove singularity to enhance the transition temperature T$_c$ is reduced by disorder it is not eliminated. In fact we give a qualitative account of changes in the T$_c$ vs. doping curve with increasing disorder and compare our results with experiments on the Y_{0.8}Ca_{0.2}Ba_2(Cu_{1-c}Zn_c)_{3}O_{7-\delta} alloys.