Coexistence of Chiral Majorana Edge States and Bogoliubov Fermi Surfaces in Two-Dimensional Nonsymmorphic Dirac Semimetal/Superconductor Heterostructures

TL;DR

This paper explores a 2D nonsymmorphic Dirac semimetal/superconductor heterostructure, revealing coexistence of chiral Majorana edge states and Bogoliubov Fermi surfaces, with implications for topological quantum phases and thermal Hall effects.

Contribution

It demonstrates the realization of topological Bogoliubov Fermi surfaces and coexistence with chiral Majorana edge states in a 2D Dirac semimetal/superconductor system, a novel phase not previously identified.

Findings

Out-of-plane Zeeman field induces Chern insulator phase with chiral edge states.

Proximity to s-wave superconductor yields chiral topological superconductors with large Chern numbers.

Bogoliubov Fermi surfaces coexist with chiral Majorana edge states, affecting thermal Hall responses.

Abstract

Dirac semimetals are renowned for the host of singular symmetry-protected band degeneracies which can give rise to other exotic phases. In this work, we consider a two-dimensional Dirac semimetal stabilized by PT symmetry and nonsymmorphic symmetries. We find that an out-of-plane Zeeman field can lift the Dirac points and transform the system into a Chern insulator with chiral edge states. By placing the nonsymmorphic Dirac semimetal in proximity to an s-wave superconductor, we uncover that chiral topological superconductors with large Chern numbers can be achieved. In addition, we find that topologically-protected Bogoliubov Fermi surface can also emerge in this system, due to the coexistence of inversion symmetry and particle-hole symmetry. Notably, we find that the chiral Majorana edge state persists even when the Chern number becomes ill-defined due to the appearance of Bogoliubov Fermi surfaces. The impact of these Bogoliubov Fermi surfaces on the thermal Hall effects is also investigated. Our study not only identifies a class of materials capable of realizing topological Bogoliubov Fermi surfaces through conventional s-wave superconductivity, but also uncovers an exotic phase where chiral Majorana edge states and Bogoliubov Fermi surfaces coexist.