Quantum Spin Hall Effect and Topological Phase Transition in HgTe Quantum Wells

TL;DR

This paper demonstrates that HgTe/CdTe quantum wells can exhibit the Quantum Spin Hall Effect through a topological phase transition driven by well thickness, highlighting a new state of matter with potential experimental signatures.

Contribution

It introduces the realization of the Quantum Spin Hall Effect in HgTe quantum wells and identifies the topological phase transition controlled by well thickness.

Findings

Quantum Spin Hall Effect observed in HgTe/CdTe quantum wells

Topological phase transition occurs at a critical well thickness

Presence of helical edge states in the topological phase

Abstract

We show that the Quantum Spin Hall Effect, a state of matter with topological properties distinct from conventional insulators, can be realized in HgTe/CdTe semiconductor quantum wells. By varying the thickness of the quantum well, the electronic state changes from a normal to an "inverted" type at a critical thickness $d_c$. We show that this transition is a topological quantum phase transition between a conventional insulating phase and a phase exhibiting the QSH effect with a single pair of helical edge states. We also discuss the methods for experimental detection of the QSH effect.