Anderson Topological Superconductor

TL;DR

This study investigates how disorder affects topological phases in a superconductor with spin-orbit coupling, revealing a disorder-induced topological phase with an intermediate Chern number state.

Contribution

It introduces a comprehensive analysis of topological phase transitions in disordered superconductors using multiple methods, uncovering a novel disorder-induced topological phase.

Findings

Disorder induces an intermediate topological phase with C=3

Real-space Chern number detects the phase transition from C=4 to C=3

Entanglement entropy does not detect the transition from C=4 to C=3

Abstract

In this paper we study the phase diagram of a disordered, spin-orbit coupled superconductor with $s$-wave or $d+id$-wave pairing symmetry in symmetry class $D$. We analyze the topological phase transitions by applying three different methods which include a disorder averaged entanglement entropy, a disorder averaged real-space Chern number, and an evaluation of the momentum space Chern number in a disorder averaged effective model. We find evidence for a disorder-induced topological state. While in the clean limit there is a single phase transition from a trivial phase with a Chern number $C=4$ to a topological phase with $C=1$, in the disordered system there is an intermediate phase with $C=3$. The phase transition from the trivial $C=4$ phase into the intermediate phase with $C=3$ is seen in the real-space calculation of the Chern number. In spite of this, this phase transition is not detectable in the entanglement entropy. A second phase transition from the disorder induced $C=3$ into the $C=1$ phase is seen in all three quantities.