Deciphering Chiral Superconductivity via Impurity Bound States

TL;DR

This paper introduces a novel real-space diagnostic based on impurity-induced bound states to identify chiral superconductivity, leveraging symmetry properties to distinguish these states at the atomic scale.

Contribution

It analytically and numerically demonstrates a unique asymmetry in impurity bound states as a signature of chiral superconductivity, applicable to various systems.

Findings

Impurity bound states exhibit asymmetric local density of states in chiral superconductors.

The asymmetry is rooted in pairing chirality and crystalline symmetry.

The diagnostic persists in multiband and extended impurity scenarios.

Abstract

Determining the symmetry of Cooper pairs remains a central challenge in the study of unconventional superconductors, particularly for chiral states that spontaneously break time-reversal symmetry. Here we demonstrate that point-like impurities in chiral superconductors generate in-gap bound states with a distinctive asymmetry: the local density of states at the impurity site vanishes at one bound-state energy, but not at its particle-hole conjugate. We prove this behavior analytically in generic two-dimensional, single-band chiral superconductors, showing it arises from a fundamental interplay between pairing chirality and crystalline rotation symmetry. Our numerical simulations confirm that this diagnostic feature persists in multiband systems and for spatially extended impurities. Our results establish a symmetry-enforced real-space diagnostic for chiral superconductivity at the atomic scale.