Gap Renormalization in Dirty Anisotropic Superconductors: Implications for the Order Parameter of the Cuprates

TL;DR

This paper investigates how non-magnetic impurities differently affect d-wave and highly anisotropic s-wave superconductors, providing insights to distinguish their order parameters using spectroscopic techniques.

Contribution

It introduces a detailed comparison of impurity effects on d-wave and anisotropic s-wave superconductors, highlighting a method to differentiate their order parameters.

Findings

Impurity-induced off-diagonal self-energy gaps out low-energy excitations in anisotropic s-wave superconductors.

The impurity response of the density of states differs significantly between d-wave and anisotropic s-wave states.

High-resolution photoemission spectra can be used to distinguish the superconducting order parameter types.

Abstract

We contrast the effects of non-magnetic impurities on the properties of superconductors having a \dw\ order parameter, and a highly anisotropic s-wave (ASW) gap with the same nodal structure. The non-vanishing, impurity induced, off-diagonal self-energy in the ASW state is shown to gap out the low energy excitations present in the clean system, leading to a qualitatively different impurity response of the single particle density of states compared to the \dw\ state. We discuss how this behaviour can be employed to distinguish one state from the other by an analysis of high-resolution angle-resolved photoemission spectra.