TY - JOUR A1 - König, Markus A1 - Baenninger, Matthias A1 - Garcia, Andrei G. F. A1 - Harjee, Nahid A1 - Pruitt, Beth L. A1 - Ames, C. A1 - Leubner, Philipp A1 - Brüne, Christoph A1 - Buhmann, Hartmut A1 - Molenkamp, Laurens W. A1 - Goldhaber-Gordon, David T1 - Spatially Resolved Study of Backscattering in the Quantum Spin Hall State JF - Physical Review X N2 - The discovery of the quantum spin Hall (QSH) state, and topological insulators in general, has sparked strong experimental efforts. Transport studies of the quantum spin Hall state have confirmed the presence of edge states, showed ballistic edge transport in micron-sized samples, and demonstrated the spin polarization of the helical edge states. While these experiments have confirmed the broad theoretical model, the properties of the QSH edge states have not yet been investigated on a local scale. Using scanning gate microscopy to perturb the QSH edge states on a submicron scale, we identify well-localized scattering sites which likely limit the expected nondissipative transport in the helical edge channels. In the micron-sized regions between the scattering sites, the edge states appear to propagate unperturbed, as expected for an ideal QSH system, and are found to be robust against weak induced potential fluctuations. KW - mesoscopics KW - topological insulators KW - transport KW - charge KW - wells KW - branched flow KW - nanostructures Y1 - 2013 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-127225 SN - 2160-3308 VL - 3 IS - 2 ER - TY - JOUR A1 - Oostinga, Jeroen B. A1 - Maier, Luis A1 - Schüffelgen, Peter A1 - Knott, Daniel A1 - Ames, Christopher A1 - Brüne, Christoph A1 - Tkachov, Grigory A1 - Buhmann, Hartmut A1 - Molenkamp, Laurens W. T1 - Josephson Supercurrent through the Topological Surface States of Strained Bulk HgTe JF - Physical Review X N2 - Strained bulk HgTe is a three-dimensional topological insulator, whose surface electrons have a high mobility (~ 30 000 cm\(^2\)=Vs), while its bulk is effectively free of mobile charge carriers. These properties enable a study of transport through its unconventional surface states without being hindered by a parallel bulk conductance. Here, we show transport experiments on HgTe-based Josephson junctions to investigate the appearance of the predicted Majorana states at the interface between a topological insulator and a superconductor. Interestingly, we observe a dissipationless supercurrent flow through the topological surface states of HgTe. The current-voltage characteristics are hysteretic at temperatures below 1 K, with critical supercurrents of several microamperes. Moreover, we observe a magnetic-field-induced Fraunhofer pattern of the critical supercurrent, indicating a dominant \(2\pi\)-periodic Josephson effect in the unconventional surface states. Our results show that strained bulk HgTe is a promising material system to get a better understanding of the Josephson effect in topological surface states, and to search for the manifestation of zero-energy Majorana states in transport experiments. KW - topological insulators KW - mesoscopics KW - superconductivity Y1 - 2013 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-129834 VL - 3 IS - 021007 ER - TY - JOUR A1 - Brüne, Christoph A1 - Thienel, Cornelius A1 - Stuiber, Michael A1 - Böttcher, Jan A1 - Buhmann, Hartmut A1 - Novik, Elena G. A1 - Liu, Chao-Xing A1 - Hankiewicz, Ewelina M. A1 - Molenkamp, Laurens W. T1 - Dirac-Screening Stabilized Surface-State Transport in a Topological Insulator JF - Physical Review X N2 - We report magnetotransport studies on a gated strained HgTe device. This material is a three-dimensional 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 (3×1011  cm−2