Characterizing unconventional superconductors from the spin structure of impurity-induced bound states

TL;DR

This paper investigates the spin structure of impurity-induced bound states in two-dimensional unconventional superconductors with broken inversion symmetry, revealing signatures that distinguish topological phases and identify pairing types.

Contribution

It introduces a method to characterize unconventional superconductors by analyzing the spin polarization of impurity bound states, aiding in identifying topological phases and pairing symmetries.

Findings

Spin polarization signatures differentiate topological from non-topological phases.

Spin-polarized STM can determine the spin-triplet pairing vector.

Method enables distinguishing between different unconventional pairing types.

Abstract

Cooper pairs in two-dimensional unconventional superconductors with broken inversion symmetry are in a mixture of an even-parity spin-singlet pairing state with an odd-parity spin-triplet pairing state. We study the magnetic properties of the impurity bound states in such superconductors and find striking signatures in their spin polarization which allow to unambiguously discriminate a non-topological superconducting phase from a topological one. Moreover, we show how these properties, which could be measured using spin-polarized scanning tunneling microscopy (STM), also enable to determine the direction of the spin-triplet pairing vector of the host material and thus to distinguish between different types of unconventional pairing.