Suppression of surface p-wave superconductivity in disordered topological insulators

TL;DR

This paper investigates how disorder affects surface p-wave superconductivity in topological insulators, showing that increased disorder suppresses p-wave pairing, leading to predominantly s-wave superconductivity.

Contribution

It provides a self-consistent Green function analysis revealing the suppression of p-wave pairing in disordered TIs and clarifies the role of mean-free path in the induced superconductivity.

Findings

P-wave component is suppressed in dirty TIs with short mean-free paths.

Induced superconductivity becomes predominantly s-wave in disordered systems.

Cleaner TIs can have comparable p- and s-wave pairing magnitudes.

Abstract

The paper proposes a self-consistent Green function description of the induced surface superconductivity in a disordered three-dimensional topological insulator (TI) coupled to an s-wave superconductor. We recover earlier results regarding the induced spin-triplet p-wave pairing, showing that a mixture of p- and s-wave pair correlations appears as a result of broken spin-rotation symmetry on the helical surface of the TI. Unlike the s-wave pairing, the p-wave component is found to be suppressed in dirty TIs in which the elastic mean-free path is much smaller than the superconducting coherence length. The suppression is due to the generic nonlocality of the spin-triplet correlations, which makes them strongly dependent on the mean-free path in a disordered system. In dirty TIs the induced superconductivity is predicted to be predominantly s-wave like. In cleaner TIs, however, the p-wave component may reach a magnitude comparable with (but not larger than) the s-wave pairing.