The local spectrum of a superconductor as a probe of interactions between magnetic impurities

TL;DR

This paper investigates how the local electronic spectrum of a superconductor reveals the nature of magnetic impurity interactions, proposing a new spectroscopy method to distinguish parallel and antiparallel impurity alignments.

Contribution

It introduces a novel nonmagnetic scanning tunneling spectroscopy technique to differentiate magnetic impurity interactions based on spectral features.

Findings

Parallel impurity pairs form hybridized mid-gap states

Antiparallel impurity pairs have degenerate states

Spectral differences can identify impurity alignments

Abstract

Qualitative differences in the spectrum of a superconductor near magnetic impurity pairs with moments aligned parallel and antiparallel are derived. A proposal is made for a new, nonmagnetic scanning tunneling spectroscopy of magnetic impurity interactions based on these differences. Near parallel impurity pairs the mid-gap localized spin-polarized states associated with each impurity hybridize and form bonding and anti-bonding molecular states with different energies. For antiparallel impurity moments the states do not hybridize; they are degenerate.