@article{KoenigBaenningerGarciaetal.2013,
  author    = {K{\"o}nig, Markus and Baenninger, Matthias and Garcia, Andrei G. F. and Harjee, Nahid and Pruitt, Beth L. and Ames, C. and Leubner, Philipp and Br{\"u}ne, Christoph and Buhmann, Hartmut and Molenkamp, Laurens W. and Goldhaber-Gordon, David},
  title     = {Spatially Resolved Study of Backscattering in the Quantum Spin Hall State},
  series = {Physical Review X},
  volume    = {3},
  journal   = {Physical Review X},
  number    = {2},
  issn      = {2160-3308},
  doi       = {10.1103/PhysRevX.3.021003},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-127225},
  pages     = {21003},
  year      = {2013},
  abstract  = {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.},
  language  = {en}
}
@article{DziomShuvaevPimenovetal.2017,
  author    = {Dziom, V. and Shuvaev, A. and Pimenov, A. and Astakhov, G.V. and Ames, C. and Bendias, K. and B{\"o}ttcher, J. and Tkachov, G. and Hankiewicz, E.M. and Br{\"u}ne, C. and Buhmann, H. and Molenkamp, L.W.},
  title     = {Observation of the universal magnetoelectric effect in a 3D topological insulator},
  series = {Nature Communications},
  volume    = {8},
  journal   = {Nature Communications},
  number    = {15197},
  doi       = {10.1038/ncomms15197},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-170875},
  year      = {2017},
  abstract  = {The electrodynamics of topological insulators (TIs) is described by modified Maxwell's equations, which contain additional terms that couple an electric field to a magnetization and a magnetic field to a polarization of the medium, such that the coupling coefficient is quantized in odd multiples of α/4π per surface. Here we report on the observation of this so-called topological magnetoelectric effect. We use monochromatic terahertz (THz) spectroscopy of TI structures equipped with a semitransparent gate to selectively address surface states. In high external magnetic fields, we observe a universal Faraday rotation angle equal to the fine structure constant α=e\(^{2}\)/2E\(_{0}\)hc (in SI units) when a linearly polarized THz radiation of a certain frequency passes through the two surfaces of a strained HgTe 3D TI. These experiments give insight into axion electrodynamics of TIs and may potentially be used for a metrological definition of the three basic physical constants.},
  language  = {en}
}
@article{WiedenmannBocquillonDeaconetal.2016,
  author    = {Wiedenmann, J. and Bocquillon, E. and Deacon, R.S. and Hartinger, S. and Herrmann, O. and Klapwijk, T.M. and Maier, L. and Ames, C. and Br{\"u}ne, C. and Gould, C. and Oiwa, A. and Ishibashi, K. and Tarucha, S. and Buhmann, H. and Molenkamp, L.W.},
  title     = {4π-periodic Josephson supercurrent in HgTe-based topological Josephson junctions},
  series = {Nature Communications},
  volume    = {7},
  journal   = {Nature Communications},
  doi       = {10.1038/ncomms10303},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-175353},
  year      = {2016},
  abstract  = {The Josephson effect describes the generic appearance of a supercurrent in a weak link between two superconductors. Its exact physical nature deeply influences the properties of the supercurrent. In recent years, considerable efforts have focused on the coupling of superconductors to the surface states of a three-dimensional topological insulator. In such a material, an unconventional induced p-wave superconductivity should occur, with a doublet of topologically protected gapless Andreev bound states, whose energies vary 4π-periodically with the superconducting phase difference across the junction. In this article, we report the observation of an anomalous response to rf irradiation in a Josephson junction made of a HgTe weak link. The response is understood as due to a 4π-periodic contribution to the supercurrent, and its amplitude is compatible with the expected contribution of a gapless Andreev doublet. Our work opens the way to more elaborate experiments to investigate the induced superconductivity in a three-dimensional insulator.},
  language  = {en}
}