Berlin 2012 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 28: Focus Session: Topological Insulators (jointly with MA, TT)

HL 28.1: Talk

Tuesday, March 27, 2012, 09:30–09:45, ER 164

Edge channel mixing in HgTe/HgCdTe Quantum point contacts — •Mathias J. Mühlbauer, Timo Wagner, Philipp Leubner, Christopher Ames, Christoph Brüne, Hartmut Buhmann, and Laurens W. Molenkamp — Physikalisches Institut (EP3), Universität Würzburg, 97074 Würzburg, Germany

In this project we study the properties of Quantum Point Contacts (QPCs) that were fabricated in HgTe/HgCdTe high mobility inverted quantum well structures, using e-beam lithography and dry-etching techniques. However, the realization of QPCs in these structures is not trivial due to the narrow band gap and the presence of the Quantum Spin Hall Effect (QSHE) [1]. We demonstrate that these structures are controllable using top gate electrodes and confirm this by low temperature conductance measurements at 4 K and 1.8 K, which indicate steps in 2e²/h. The residual conductance in these measurements can be explained by the helical Quantum Spin Hall edge channels which are still present during the transition from the n-conducting region to the p-conducting part. Deviations of ideal conductance plateau values could be explained with the changing transmission probability due to the mixing of these channels because of their finite extension [2].

[1] M. König, S. Wiedmann, C. Brüne, A. Roth, H. Buhmann, L. W. Molenkamp, X-L. Qi, S. C. Zhang, Science, 318, 766, (2007).

[2] Zhou, B., Lu, H-Z., Chu, R-L., Shen, S-Q. & Niu, Q., Phys. Rev. Lett. 101, 246807 (2008)