# Second-order Topological Superconductors with Mixed Pairing

## TL;DR

This paper demonstrates that a 2D Rashba semiconductor with mixed even-parity pairing can host second-order topological superconductivity, featuring Majorana zero modes at corners, with phase boundaries determined by Fermi surface and nodal point relations.

## Contribution

It introduces a new second-order topological superconducting phase in Rashba semiconductors with mixed pairing, providing a phase boundary criterion and experimental proposals.

## Key findings

- Corner Majorana zero modes in the second-order phase
- Phase boundaries determined by Fermi surface and nodal point positions
- Proposed experimental setups for realizing the phase

## Abstract

We show that a two-dimensional semiconductor with Rashba spin-orbit coupling could be driven into the second-order topological superconducting phase when a mixed-pairing state is introduced. The superconducting order we consider involves only even-parity components and meanwhile breaks time-reversal symmetry. As a result, each corner of a square-shaped Rashba semiconductor would host one single Majorana zero mode in the second-order nontrivial phase. Starting from edge physics, we are able to determine the phase boundaries accurately. A simple criterion for the second-order phase is further established, which concerns the relative position between Fermi surfaces and nodal points of the superconducting order parameter. In the end, we propose two setups that may bring this mixed-pairing state into the Rashba semiconductor, followed by a brief discussion on the experimental feasibility of the two platforms.