Effect of transverse electric field on helical edge states in a quantum spin-Hall system

We study the electronic band, density distribution, and transport property for a HgTe/CdTe quantum well Hall bar with finite-width in the presence of a transverse electric field. It is found that the electric field can lead to a topological phase transition which controls edge state properties. Interestingly, the chirality of edge states can be modified under electric field, and a sufficient high field can remove the spectrum gap induced by the coupling between the edge states in a narrow Hall bar, restoring quantum spin-Hall effect. These findings may provide a fundamental understanding of topological edge states. (C) 2011 American Institute of Physics. [doi:10.1063/1.3664776]