# Inversion-protected higher order topological superconductivity in monolayer WTe$_2$

## TL;DR

This paper predicts that monolayer WTe$_2$ can host higher-order topological superconductivity with Majorana corner modes, driven by its inversion symmetry and boundary properties, offering a new platform for topological quantum computation.

## Contribution

The study introduces a microscopic model showing Majorana corner modes in monolayer WTe$_2$, revealing a new class of inversion-protected higher-order topological superconductors.

## Key findings

- Majorana corner modes found in spin-triplet phases.
- In-plane magnetic field stabilizes unconventional pairing with Majorana modes.
- Proposes monolayer WTe$_2$ as a platform for higher-order topological superconductivity.

## Abstract

Monolayer WTe$_2$, a centrosymmetric transition metal dichacogenide, has recently been established as a quantum spin Hall insulator and found superconducting upon gating. Here we study the pairing symmetry and topological nature of superconducting WTe$_2$ with a microscopic model at mean-field level. Surprisingly, we find that the spin-triplet phases in our phase diagram all host Majorana modes localized on two opposite corners. Even when the conventional pairing is favored, we find that an intermediate in-plane magnetic field exceeding the Pauli limit stabilizes an unconventional equal-spin pairing aligning with the field, which also hosts Majorana corner modes. Motivated by our findings, we obtain a recipe for two-dimensional superconductors featuring "higher-order topology" from the boundary perspective: Generally a superconducting inversion-symmetric quantum spin Hall material whose normal-state Fermi surface is away from high-symmetry points, such as gated monolayer WTe$_2$, hosts Majorana corner modes if the superconductivity is parity-odd. We further point out that this higher-order phase is an inversion-protected topological crystalline superconductor and study the bulk-boundary correspondence. Finally, we discuss possible experiments for probing the Majorana corner modes. Our findings suggest superconducting monolayer WTe$_2$ is a playground for higher-order topological superconductivity, and possibly the first material realization for inversion-protected Majorana corner modes without utilizing proximity effect.