Disorder Effects in Superconductors with Anisotropic Pairing: From Cooper Pairs to Compact Bosons

TL;DR

This paper investigates how disorder affects superconductors with anisotropic pairing, revealing a crossover from BCS pairs to compact bosons and showing increased stability of d-wave pairing at strong disorder levels.

Contribution

It introduces a crossover framework from weak to strong coupling in anisotropic superconductors, explaining the stability of d-wave pairing under disorder.

Findings

Increased pairing strength leads to deviation from Abrikosov-Gorkov law.

Superconductors with d-wave pairing become more stable with stronger disorder.

High-T_c superconductors' intermediate pairing regime explains their disorder resilience.

Abstract

In the weak coupling BCS-approximation normal impurities do not influence superconducting T_{c} in significant manner in case of isotropic s-wave pairing. However, in case of d-wave pairing these are strongly pair-breaking. This fact is in rather strong contradiction with many experiments on disordered high-T_{c} superconductors assuming the d-wave nature of pairing in these systems. With the growth of electron attraction within the Cooper pair the system smoothly crosses over from BCS-pairs to compact Boson picture of superconductivity. As pairing strength grows and pairs become compact significant deviations from universal Abrikosov-Gorkov dependence of T_{c} on disorder appear in case of d-wave pairing with superconducting state becoming more stable than in the weak coupling case. As high-T_{c} superconductors are actually in the intermediate region with Cooper pairs size of the order of few interatomic lengths, these results can explain the relative stability of d-wave pairing under rather strong disordering.