Chiral Majorana fermions in graphene from proximity-induced superconductivity

Abstract

We present a detailed theoretical study of chiral topological superconductor phases in proximity-superconducting graphene systems based on an effective model inspired by density functional theory simulations. Inducing $s$-wave superconductivity in quantum anomalous Hall effect systems leads to chiral topological superconductors. For out-of-plane magnetization we find topological superconducting phases with even numbers of chiral Majorana fermions per edge, which is correlated with the opening of a nontrivial gap in the bulk system in the $K$ points and their connection under particle-hole symmetry. We show that in a quantum anomalous Hall insulator with in-plane magnetization and a nontrivial gap opening at $M$, the corresponding topological superconductor can be tuned to host only single chiral Majorana states at its edge, which is promising for proposals exploiting such states for braiding operations.