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End date: 2024 × Start date: 2020 × End date: 2024 × Start date: 2020 × Publisher: Weinheim : Wiley-VCH × Subject: 3D topological insulators × WGL Institute: IFWD ×

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    Density-Dependence of Surface Transport in Tellurium-Enriched Nanograined Bulk Bi2Te3
    (Weinheim : Wiley-VCH, 2023) Izadi, Sepideh; Bhattacharya, Ahana; Salloum, Sarah; Han, Jeong Woo; Schnatmann, Lauritz; Wolff, Ulrike; Perez, Nicolas; Bendt, Georg; Ennen, Inga; Hütten, Andreas; Nielsch, Kornelius; Schulz, Stephan; Mittendorff, Martin; Schierning, Gabi
    Three-dimensional topological insulators (3D TI) exhibit conventional parabolic bulk bands and protected Dirac surface states. A thorough investigation of the different transport channels provided by the bulk and surface carriers using macroscopic samples may provide a path toward accessing superior surface transport properties. Bi2Te3 materials make promising 3D TI models; however, due to their complicated defect chemistry, these materials have a high number of charge carriers in the bulk that dominate the transport, even as nanograined structures. To partially control the bulk charge carrier density, herein the synthesis of Te-enriched Bi2Te3 nanoparticles is reported. The resulting nanoparticles are compacted into nanograined pellets of varying porosity to tailor the surface-to-volume ratio, thereby emphasizing the surface transport channels. The nanograined pellets are characterized by a combination of resistivity, Hall- and magneto-conductance measurements together with (THz) time-domain reflectivity measurements. Using the Hikami-Larkin-Nagaoka (HLN) model, a characteristic coherence length of ≈200 nm is reported that is considerably larger than the diameter of the nanograins. The different contributions from the bulk and surface carriers are disentangled by THz spectroscopy, thus emphasizing the dominant role of the surface carriers. The results strongly suggest that the surface transport carriers have overcome the hindrance imposed by nanoparticle boundaries.
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    Quantum Transport in Nanostructures of 3D Topological Insulators
    (Weinheim : Wiley-VCH, 2020) Giraud, Romain; Dufouleur, Joseph
    Quantum transport measurement is an efficient tool to unveil properties of topological surface states in 3D topological insulators. Herein, experimental and theoretical results are reviewed, presenting first some methods for the growth of nanostructures. The effect of the disorder and the band bending is discussed in details both experimentally and theoretically. Then, the focus is put on disorder and quantum confinement effect in topological surface states of 3D topological insulators narrow nanostructures. Such effect can be revealed by investigating quantum interferences at very low temperature such as Aharonov–Bohm oscillations or universal conductance fluctuations. © 2020 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim