Massive and Topological Surface States in Tensile-Strained HgTe.

Mahler, David M; Müller, Valentin L; Thienel, Cornelius; Wiedenmann, Jonas; Beugeling, Wouter; Buhmann, Hartmut; Molenkamp, Laurens W · Nano Lett · 2021

basic_science · Level V

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Abstract

Magneto-transport measurements on gated high-mobility heterostructures containing a 60 nm layer of tensile-strained HgTe, a three-dimensional topological insulator, show well-developed Hall quantization from surface states both in the n- as well as in the p-type regime. While the n-type behavior is due to transport in the topological surface state of the material, we find from 8-orbital <i>k</i>·<i>p</i> calculations that the p-type transport results from massive Volkov-Pankratov states. Their formation prevents the Dirac point and thus the p-conducting topological surface state from being accessible in transport experiments. This interpretation is supported by low-field magneto-transport experiments demonstrating the coexistence of n-conducting topological surface states and p-conducting Volkov-Pankratov states at the relevant gate voltages.