Bulk Band Gap and Surface State Conduction Observed in Voltage-Tuned Crystals of the Topological Insulator ${\mathrm{Bi}}_{2}{\mathrm{Se}}_{3}$

Bulk Band Gap and Surface State Conduction Observed in Voltage-Tuned Crystals of the Topological Insulator ${Bi}_{2} {Se}_{3}$

J. G. Checkelsky, Y. S. Hor, R. J. Cava, and N. P. Ong

Phys. Rev. Lett. 106, 196801 – Published 10 May 2011

Abstract

We report a transport study of exfoliated few monolayer crystals of topological insulator ${Bi}_{2} {Se}_{3}$ in an electric field effect geometry. By doping the bulk crystals with Ca, we are able to fabricate devices with sufficiently low bulk carrier density to change the sign of the Hall density with the gate voltage $V_{g}$ . We find that the temperature $T$ and magnetic field dependent transport properties in the vicinity of this $V_{g}$ can be explained by a bulk channel with activation gap of approximately 50 meV and a relatively high-mobility metallic channel that dominates at low $T$ . The conductance (approximately $2 \times 7 e^{2} / h$ ), weak antilocalization, and metallic resistance-temperature profile of the latter lead us to identify it with the protected surface state. The relative smallness of the observed gap implies limitations for electric field effect topological insulator devices at room temperature.

Received 7 December 2010

DOI:https://doi.org/10.1103/PhysRevLett.106.196801

Authors & Affiliations

J. G. Checkelsky^1,*, Y. S. Hor^2,†, R. J. Cava², and N. P. Ong¹

¹Department of Physics, Princeton University, New Jersey 08544, USA
²Department of Chemistry, Princeton University, New Jersey 08544, USA

^*Present address: Advanced Science Institute, RIKEN, Saitama, Japan 351-0198.
^†Present address: Department of Physics, Missouri University of Science and Technology, Rolla, MO 65409, USA.