Spin-polarized zero-bias peak from a single magnetic impurity at an s-wave superconductor: first-principles study

TL;DR

This study uses first-principles simulations to explore how spin-orbit coupling influences the formation of spin-polarized zero-bias peaks from single magnetic impurities on superconducting Pb surfaces, relevant for topological quantum states.

Contribution

It provides a detailed first-principles analysis of YSR states with SOC, revealing conditions for spin-polarized ZBPs from single magnetic impurities, advancing understanding beyond effective models.

Findings

Strong SOC induces spin-polarized ZBPs with impurity magnetic moment rotation.

ZBPs from Fe and Co impurities exhibit large spin polarization.

Results inform conditions for topological states in atomic chains.

Abstract

Magnetic impurities at surfaces of superconductors can induce bound states referred to as Yu-Shiba-Rusinov (YSR) states within superconducting gaps. Understanding of YSR states with spin-orbit coupling (SOC) plays a pivotal role in studies of Majorana zero modes. Spin polarization of a zero-bias peak (ZBP) is used to determine its topological nature. Here we investigate the YSR states of single magnetic impurities at the surface of Pb using the fully relativistic first-principles simulations including band structure of Pb and five 3$d$ orbitals of the impurity in the superconducting state. We show that for single Fe and Co impurities, strong SOC can induce a ZBP with rotation of the impurity magnetic moment and that the ZBP has large spin polarization in contrast to effective model studies. Conditions for a ZBP from a single magnetic impurity are discussed. Our results are relevant to longer atomic chains considering their canting and noncollinear magnetism.