Abstract
The effective matrix Hamiltonian for two-dimensional states in HgTe/CdTe quantum wells is derived. The use of the extended basis (in contrast to the previously studied matrix Hamiltonian) allows us to describe quantum wells with arbitrary orientation of interfaces and investigate the influence of in-plane magnetic field. The Hamiltonian is applied to calculation of energy spectra of both two-dimensional subbands and edge states in the range of well widths corresponding to the topological insulator phase. It is found that the in-plane magnetic field opens a gap in the edge-state spectrum, and the increase in the field causes disappearance of one of the edge-state branches. A strong (about 10 T) magnetic field induces a phase transition from the gapped state to a gapless two-dimensional state, with energy spectrum similar to that of bulk HgTe. An analytical expression for the transition field through the parameters of the effective Hamiltonian is obtained.
1 More- Received 30 October 2011
DOI:https://doi.org/10.1103/PhysRevB.85.045310
©2012 American Physical Society