Impurity induced double transitions for accidentally degenerate unconventional pairing states

TL;DR

This paper explores how non-magnetic impurities can cause double superconducting transitions in unconventional pairing states, with implications for detecting such states in materials like Sr$_2$RuO$_4$.

Contribution

It demonstrates how impurity-induced lifting of degeneracy can lead to observable double transitions in unconventional superconductors.

Findings

Impurities can induce double transitions in certain pairing states.

The behavior depends on specific material parameters.

Detection methods for these transitions are proposed.

Abstract

Non-magnetic impurities can lift the accidental degeneracy of unconventional pairing states, such as the $(d + i g)$-wave state recently proposed for Sr$_2$RuO$_4$. This type of effect would lead to a superconducting double transition upon impurity doping. In a model calculation it is shown how this behavior depends on material parameters and how it could be detected.