Three-dimensional phase diagram of disordered HgTe/CdTe Quantum spin-Hall wells

TL;DR

This paper maps the 3D phase diagram of disordered HgTe/CdTe quantum wells, revealing the interplay of Quantum spin-Hall, metallic, and insulating phases, and clarifying the nature of the topological Anderson insulator.

Contribution

It provides the first comprehensive 3D phase diagram including disorder effects, showing TAI as part of the Quantum spin-Hall phase rather than a separate phase.

Findings

Disorder deforms the Quantum spin-Hall phase boundary.

TAI is not a distinct phase but part of the Quantum spin-Hall phase.

The phase diagram includes Quantum spin-Hall, metallic, and normal insulating phases.

Abstract

We compute the phase diagram of the HgTe/CdTe quantum wells in the 3 dimensional (3D) parameter space of Dirac mass, Fermi level and disorder strength. The phase diagram reveals the Quantum spin-Hall, the metallic and the normal insulating phases. The phase boundary of the Quantum spin-Hall state is shown to be strongly deformed by the disorder. Taking specific cuts into this 3D phase diagram, we recover the so called topological Anderson insulator (TAI) phase, but now we can demonstrate explicitly that TAI is not a distinct phase and instead it is part of the Quantum spin-Hall phase. The calculations are performed with $S_z$-conserving and $S_z$-nonconserving Hamiltonians.