Unveiling odd-frequency pairing around a magnetic impurity in a superconductor

TL;DR

This paper investigates how a magnetic impurity in a conventional superconductor induces unconventional odd-frequency pairing correlations, supported by theoretical derivations and experimental evidence from STM data.

Contribution

It derives an exact relation linking local density of states and odd-frequency pairing, and provides experimental evidence of odd-frequency pairing in a Pb/Si(111) system.

Findings

Experimental evidence of odd-frequency pairing around magnetic impurities

Derived a proportionality relation between density of states and odd-frequency pairing

Extracted the odd-frequency superconducting function from STM spectra

Abstract

We study the unconventional superconducting correlations caused by a single isolated magnetic impurity in a conventional s-wave superconductor. Due to the local breaking of time-reversal symmetry, the impurity induces unconventional superconductivity which is even in both space and spin variables but odd under time inversion. We derive an exact proportionality relation between the even-frequency component of the local electron density of states and the imaginary part of the odd-frequency local pairing function. By applying this relation to scanning tunneling microscopy spectra taken on top of magnetic impurities immersed in a Pb/Si(111) monolayer, we show experimental evidence of the occurrence of the odd-frequency pairing in these systems and explicitly extract its superconducting function from the data.