Disorder-induced phase transition in Dirac systems beyond the linear approximation

TL;DR

This paper studies how short-range disorder impacts the band-gap and topological phases in two-dimensional Dirac systems with higher-order momentum terms, revealing effects beyond the linear approximation.

Contribution

It introduces a self-consistent approach to analyze disorder effects in Dirac systems with quadratic corrections, extending beyond the traditional BHZ model.

Findings

Disorder affects the band-gap even in gapless systems due to quadratic terms.

Disorder can induce topological phase transitions in realistic HgTe quantum wells.

Differences between simplified models and real structures are significant for disorder effects.

Abstract

By using the self-consistent Born approximation, we investigate disorder effect induced by the short-range impurities on the band-gap in two-dimensional Dirac systems with the higher order terms in momentum. Starting from the Bernevig-Hughes-Zhang (BHZ) model, we calculate the density-of-states as a function of the disorder strength. We show that due to quadratic corrections to the Dirac Hamiltonian, the band-gap is always affected by the disorder even if the system is gapless in the clean limit. Finally, we explore the disorder effects by using an advanced effective Hamiltonian describing the side maxima of the valence subband in HgTe~quantum wells. We show that the band-gap and disorder-induced topological phase transition in the real structures may differ significantly from those predicted within the BHZ model.