Majorana corner modes in an s-wave second order topological superfluid

Abstract

In sharp contrast to conventional topological superfluids, higher order (order r > 1) topological superfluids in n dimensions do not host n − 1 dimensional Majorana boundary states, instead host n − r dimensional Majorana excitations. In this paper, we propose Majorana corner modes can emerge in a second order superfluid with s-wave pairing, instead of unconventional pairings such as d-wave and -wave pairings in most of previous proposals. There are three key ingredients in this scheme consisting of a topological insulator, an in-plane Zeeman field, and an s-wave pairing. Based on the low energy theory for edge states, where the effective Dirac mass sign changes at the corner, we unveil the emergence of Majorana corner modes. Our proposal provides a promising platform for implementing 2D second order topological superfluids and Majorana corner modes.