Scattering by impurity-induced order parameter ``holes'' in d-wave superconductors

TL;DR

This paper studies how nonmagnetic impurities create local suppressions in the order parameter of d-wave superconductors, leading to observable effects like spectral features and increased sensitivity of physical properties to disorder.

Contribution

It introduces a self-consistent t-matrix approach to model impurity-induced order parameter 'holes' as off-diagonal scatterers in d-wave superconductors, revealing new spectral and physical effects.

Findings

Finite-energy spectral features in the impurity band

Enhanced low-temperature microwave absorption

Increased sensitivity of London penetration depth to disorder

Abstract

Nonmagnetic impurities in d-wave superconductors cause strong local suppressions of the order parameter. We investigate the observable effects of the scatterigng off such suppressions in bulk samples by treating the order parameter "hole" as a pointlike off-diagonal scatterer treated within a self-consistent t-matrix approximation. Strong scattering potentials lead to a finite-energy spectral feature in the d-wave "impurity band", the observable effects of which include enhanced low-temperature microwave power absorption and a stronger sensitivity of the London penetration depth to disorder than found previously in simpler ``dirty'' d-wave models.