Localized Andreev edge states in HgTe quantum wells

TL;DR

This paper explores how superconductivity influences topological insulator states in HgTe quantum wells, revealing conditions under which edge states become gapped, form localized Andreev states, or merge with bulk states.

Contribution

It provides a detailed analysis of the conditions leading to different edge state behaviors in HgTe quantum wells coupled to superconductors.

Findings

Edge states can become gapped depending on coupling strength.

Localized Andreev states form under certain conditions.

TI can transition into an anisotropic narrow-gap semiconductor.

Abstract

We investigate the interplay of superconductivity and the topological order in the topological insulator (TI) formed in HgTe-CdTe quantum wells coupled to the s-wave isotropic superconductor (SC) placed on top of CdTe layer. Proximity effect induces superconducting correlations in TI effecting classification of the TI electronic states. Depending on the strength of the coupling and the initial chemical potentials in SC and TI, the edge states either (i) become gapped, or (ii) hybridize into localized Andreev states, or else (iii) merge with the bulk states turning the TI into an anisotropic narrow-gap semiconductor.