The quantum spin Hall (QSH) state is a topologically non-trivial state of quantum matter which preserves time-reversal symmetry; it has an energy gap in the bulk, but topologically robust gapless states at the edge. Recently, this novel effect has been predicted and observed in HgTe quantum wells. In this work we predict a similar effect arising in Type-II semiconductor quantum wells made from InAs/GaSb/AlSb. Because of a rare band alignment the quantum well band structure exhibits an "inverted" phase similar to CdTe/HgTe quantum wells, which is a QSH state when the Fermi level lies inside the gap. Due to the asymmetric structure of this quantum well, the effects of inversion symmetry breaking and inter-layer charge transfer are essential. By standard self-consistent calculations, we show that the QSH state persists when these corrections are included, and a quantum phase transition between the normal insulator and the QSH phase can be electrically tuned by the gate voltage.
@article{arxiv.0801.2831,
title = {Quantum Spin Hall Effect in Inverted Type II Semiconductors},
author = {Chaoxing Liu and Taylor L. Hughes and Xiao-Liang Qi and Kang Wang and Shou-Cheng Zhang},
journal= {arXiv preprint arXiv:0801.2831},
year = {2009}
}
Comments
5 pages,4 figures. Submitted to PRL. For high resolution figures see final published version when available