We report magnetotransport studies on a gated strained HgTe device. This material is a threedimensional topological insulator and exclusively shows surface state transport. Remarkably, the Landau level dispersion and the accuracy of the Hall quantization remain unchanged over a wide density range (3×1011cm−2<n<1×1012cm−2). This implies that even at large carrier densities the transport is surface state dominated, where bulk transport would have been expected to coexist already. Moreover, the density dependence of the Dirac-type quantum Hall effect allows to identify the contributions from the individual surfaces. A k⋅p model can describe the experiments, but only when assuming a steep band bending across the regions where the topological surface states are contained. This steep potential originates from the specific screening properties of Dirac systems and causes the gate voltage to influence the position of the Dirac points rather than that of the Fermi level.
@article{arxiv.1407.6537,
title = {Dirac-screening stabilized surface-state transport in a topological insulator},
author = {Christoph Brüne and Cornelius Thienel and Michael Stuiber and Jan Böttcher and Hartmut Buhmann and Elena G. Novik and Chao-Xing Liu and Ewelina M. Hankiewicz and Laurens W. Molenkamp},
journal= {arXiv preprint arXiv:1407.6537},
year = {2014}
}