Topological Yu-Shiba-Rusinov chain in monolayer transition-metal dichalcogenide superconductors

TL;DR

This paper proposes that ferromagnetic adatom chains on monolayer TMD superconductors can host one-dimensional topological superconducting states with Majorana zero modes, influenced by chain orientation and magnetic configuration.

Contribution

It introduces a new platform for realizing topological superconductivity using monolayer TMDs with magnetic adatom chains, analyzing the effects of various parameters on the topological phase.

Findings

Topological phase diagram depends on adatom spacing and magnetic moment direction.

Chain orientation relative to crystal affects topological phase.

Presence of Majorana zero modes at chain ends in certain configurations.

Abstract

Monolayers of transition-metal dichalcogenides (TMDs) are two-dimensional materials whose low energy sector consists of two inequivalent valleys. The valence bands have a large spin splitting due to strong spin-orbit coupling. Furthermore the spin is polarized up in one valley and down in the other (in directions perpendicular to the two-dimensional crystal). We focus on lightly hole-doped systems where the Fermi surface consists of two disconnected circles with opposite spins. For both proximity induced and intrinsic local attractive interaction induced superconductivity, a fully gapped intervalley pairing state is favored in this system, which is an equal superposition of the singlet and the m=0 triplet for the lack of centrosymmetry. We show that a ferromagnetically ordered magnetic-adatom chain placed on a monolayer TMD superconductor provides a platform to realize one-dimensional topological superconducting state characterized by the presence of Majorana zero modes at its ends. We obtain the topological phase diagram and show that the topological superconducting phase is affected not only by the adatom spacing and the direction of the magnetic moment, but also by the orientation of the chain relative to the crystal.