Simultaneous Electrical-Field-EffectModulation of Both Top and Bottom Dirac Surface States of EpitaxialThin Films of Three-Dimensional Topological Insulators.

Itis crucial for the studies of the transport properties and quantumeffects related to Dirac surface states of three-dimensional topologicalinsulators (3D TIs) to be able to simultaneously tune the chemicalpotentials of both top and bottom surfaces of a 3D TI thin film. Wehave realized this in molecular beam epitaxy-grown thin films of 3DTIs, as well as magnetic 3D TIs, by fabricating dual-gate structureson them. The films could be tuned between n-type and p-type by eachgate alone. Combined application of two gates can reduce the carrierdensity of a TI film to a much lower level than with only one of themand enhance the film resistance by 10 000%, implying that Fermilevel is tuned very close to the Dirac points of both top and bottomsurface states without crossing any bulk band. The result promisesapplications of 3D TIs in field effect devices. [ABSTRACT FROM AUTHOR]