Quasidisorder Induced Topology

Abstract

We study the effects of quasidisorder and Anderson disorder on a two dimensional topological superconductor with an applied external magnetic field. The cases of a $p$-wave superconductor and a noncentrosymmetric superconductor with mixed $p$ and $s$-wave pairings and Rashba spin-orbit coupling are studied. We show that, for a perpendicular magnetic field, the introduction of quasidisorder leads to the appearance of topological phases in new regions, characterised by an integer value of the Chern number. For a parallel magnetic field, we identify regimes with the appearance of new Majorana flat bands and also new unidirectional Majorana edge states, as quasidisorder is introduced. We show that the Majorana flat bands have a quantized Berry phase of $\pi$ and identify it as a topological invariant. Two topological transitions are identified and the values of the critical exponents $z$ and $\nu$ are obtained. The fractal nature of the eigenstates is discussed both for Anderson disorder and Aubry-Andr\'e disorder.