Study of Yu-Shiba-Rusinov bound states by tuning the electron density at the Fermi energy

TL;DR

This study investigates how tuning the electron density at the Fermi energy influences Yu-Shiba-Rusinov bound states in superconductors with magnetic atoms, revealing the role of potential scattering and exchange interactions.

Contribution

It provides the first detailed experimental analysis of how electron density tuning affects YSR states and the interplay of potential scattering and exchange interactions.

Findings

Sign of U can be determined by electron density tuning

U competes with exchange interaction JS in YSR formation

Insights into magnetic atom-superconductor interactions

Abstract

Magnetic atoms can break the Cooper pairs of superconductors, leading to the formation of Yu-Shiba-Rusinov (YSR) bound states inside superconducting gaps. Theory predicts that the YSR bound states can be controlled by tuning the electron density at the Fermi energy, but it has not been studied deeply. In this work, we studied the nature of YSR bound states in response to the potential scattering U by tuning the electron density at the Fermi energy. By comparing two systems, Mn-phthalocyanine molecules on Pb(111) and Co atoms on PbSe/Pb(111), we demonstrate that the sign of U can be unambiguously determined by varying the electron density at the Fermi energy. We also show that U competes with the exchange interaction JS in the formation of YSR bound states. Our work provides insights into the interactions between magnetic atoms and superconductors at a fundamental level.