Tunneling transport of electrons on the surface of a topological insulator attached with a spiral multiferroic oxide

We study the transport properties of Dirac fermions on the surface of a topological insulator attached with a spiral multiferroic oxide (SMO). For the spiral plane of the SMO parallel to the spiral axis and the surface normal, the proximity-induced exchange field causes a particle-hole asymmetry and a transmission gap near the Dirac point. The transmission gap interval depends on the spiral wave vector q. This fact together with the tunability of q by gate voltages indicates an electric switch with high on-off ratios. The dependence of the conductance on the orientation of the spiral plane is also examined. (C) 2011 American Institute of Physics. [doi:10.1063/1.3543899]