A novel platform for two-dimensional chiral topological superconductivity

TL;DR

This paper demonstrates that decorating a superconductor surface with magnetic impurities can induce chiral topological superconductivity supporting Majorana edge modes, with potential realization on Pb surfaces with ferromagnetic adatoms.

Contribution

It introduces a new platform for 2D chiral topological superconductivity using magnetic impurity lattices on superconductors, supported by analytical and numerical phase diagrams.

Findings

Magnetic impurity lattices can induce non-trivial Chern numbers in superconductors.

Ferromagnetic adatoms on Pb surfaces can realize the proposed topological phase.

Phase diagrams identify regimes supporting chiral Majorana modes.

Abstract

We show that the surface of an $s$-wave superconductor decorated with a two-dimensional lattice of magnetic impurities can exhibit chiral topological superconductivity. If impurities order ferromagnetically and the superconducting surface supports a sufficiently strong Rashba-type spin-orbit coupling, Shiba sub-gap states at impurity locations can hybridize into Bogoliubov bands with non-vanishing, sometimes large, Chern number $C$. This topological superconductor supports $C$ chiral Majorana edge modes. We construct phase diagrams for model two-dimensional superconductors, accessing the dilute and dense magnetic impurity limits analytically and the intermediate regime numerically. To address potential experimental systems, we identify stable configurations of ferromagnetic iron atoms on the Pb (111) surface and conclude that ferromagnetic adatoms on Pb surfaces can provide a versatile platform for two-dimensional topological superconductivity.