Design principles for HgTe based topological insulator devices

TL;DR

This paper theoretically investigates the properties of CdTe/HgTe/CdTe quantum wells as topological insulators, exploring how various parameters influence their behavior and proposing a device that switches states via electric fields.

Contribution

It introduces a theoretical analysis of how alloy composition, temperature, stress, and electric fields affect the topological phase transition in HgTe-based quantum wells and proposes a novel switching device.

Findings

Critical well width depends on alloy composition and external conditions.

External electric fields can switch the quantum well between normal and topological insulator states.

Temperature and stress influence the topological phase transition.

Abstract

The topological insulator properties of CdTe/HgTe/CdTe quantum wells are theoretically studied. The CdTe/HgTe/CdTe quantum well behaves as a topological insulator beyond a critical well width dimension. It is shown that if the barrier(CdTe) and well-region(HgTe) are altered by replacing them with the alloy Cd$_{x}% $Hg$_{1-x}$Te of various stoichiometries, the critical width can be changed.The critical quantum well width is shown to depend on temperature, applied stress, growth directions and external electric fields. Based on these results, a novel device concept is proposed that allows to switch between a normal semiconducting and topological insulator state through application of moderate external electric fields.