Magnetism and in-gap states of 3d transition metal atoms on superconducting Re

TL;DR

This study investigates how 3d transition metal atoms on superconducting Re influence in-gap states and magnetic properties, revealing systematic trends crucial for designing topological superconductors.

Contribution

It combines scanning tunneling spectroscopy and ab initio calculations to analyze the evolution of YSR states and magnetic anisotropy in 3d transition metals on Re.

Findings

YSR states shift through the energy gap with d-state filling

Magnetic anisotropy sign changes correlate with d-electron count

Systematic trends identify promising candidates for topological superconductivity

Abstract

Magnetic atoms on heavy-element superconducting substrates are potential building blocks for realizing topological superconductivity in one- and two-dimensional atomic arrays. Their localized magnetic moments induce so-called Yu-Shiba-Rusinov (YSR) states inside the energy gap of the substrate. In the dilute limit, where the electronic states of the array atoms are only weakly coupled, proximity of the YSR states to the Fermi energy is essential for the formation of topological superconductivity in the band of YSR states. Here, we reveal via scanning tunnel spectroscopy and ab initio calculations of a series of 3d transition metal atoms (Mn, Fe, Co) adsorbed on the heavy-element superconductor Re that the increase of the Kondo coupling and sign change in magnetic anisotropy with d-state filling is accompanied by a shift of the YSR states through the energy gap of the substrate and a crossing of the Fermi level. The uncovered systematic trends enable the identification of the most promising candidates for the realization of topological superconductivity in arrays of similar systems.