Majorana state on the surface of a disordered 3D topological insulator

TL;DR

This paper investigates the robustness of Majorana bound states on the surface of a disordered 3D topological insulator with a superconducting antidot, revealing their resilience and tunneling signatures despite disorder.

Contribution

It provides a detailed analysis of the subgap density of states and tunneling properties of Majorana states in a disordered topological insulator with a superconducting antidot, using supersymmetric sigma model techniques.

Findings

Majorana states remain robust against disorder effects.

Resonant Andreev reflection occurs at zero energy due to Majorana states.

Subgap density of states shows characteristic features influenced by disorder.

Abstract

We study low-lying electron levels in an "antidot" capturing a coreless vortex on the surface of a three-dimensional topological insulator in the presence of disorder. The surface is covered with a superconductor film with a hole of size R larger than coherence length, which induces superconductivity via proximity effect. Spectrum of electron states inside the hole is sensitive to disorder, however, topological properties of the system give rise to a robust Majorana bound state at zero energy. We calculate the subgap density of states with both energy and spatial resolution using the supersymmetric sigma model method. Tunneling into the hole region is sensitive to the Majorana level and exhibits resonant Andreev reflection at zero energy.