Theory of Multi-Orbital Topological Superconductivity in Transition Metal Dichalcogenides

TL;DR

This paper explores how multi-orbital superconductivity in transition metal dichalcogenides can lead to topological phases, influenced by symmetry breaking and electron interactions, revealing a transition from trivial to topological states.

Contribution

It introduces a multi-orbital renormalization group approach to analyze topological superconductivity in TMD monolayers with broken mirror symmetry.

Findings

Mirror symmetry breaking induces topological superconducting phases.

Transitions from trivial to topological phases with increasing symmetry breaking.

Interaction parameters determine the emergence of nodal and gapped topological states.

Abstract

We study possible superconducting states in transition metal dichalcogenide (TMD) monolayers, assuming an on-site pairing potential that includes both intra- and inter-orbital terms. We find that if the mirror symmetry with respect to the system's plane is broken (e.g., by a substrate), this type of pairing can give rise to unconventional superconductivity, including time-reversal-invariant nodal and fully gapped topological phases. Using a multi-orbital renormalization group procedure, we show how these phases may result from the interplay between the local Coulomb repulsion, Hund's rule coupling, and phonon-mediated attraction. In particular, for a range of interaction parameters, the system transitions from a trivial phase to a nodal phase and finally to a gapped topological phase upon increasing the strength of the mirror symmetry breaking term.