Regensburg 2025 – scientific programme
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HL: Fachverband Halbleiterphysik
HL 40: 2D Semiconductors and van der Waals Heterostructures IV
HL 40.4: Talk
Wednesday, March 19, 2025, 16:15–16:30, H15
Disentangling three anisotropic resistivities of the topological insulator α-Bi4Br4 — •Jonathan K. Hofmann1,2, Serhii Kovalchuk1,3, Yuqi Zhang4,5,6, Vasily Cherepanov1, Timofey Balashov1, Zhiwei Wang4,5,6, Yugui Yao4,5,6, Irek Morawski3, F. Stefan Tautz1,2, Felix Lüpke1,7, and Bert Voigtländer1,2 — 1Peter Grünberg Institut, Forschungszentrum Jülich, Germany — 2Lehrstuhl für Experimentalphysik IV A, RWTH Aachen University, Germany — 3Institute of Experimental Physics, University of Wrocław, Poland — 4Key Laboratory of Advanced Optoelectronic Quantum Architecture and Measurement, Ministry of Education, School of Physics, Beijing Institute of Technology, China — 5Beijing Key Lab of Nanophotonics and Ultrafine Optoelectronic Systems, Beijing Institute of Technology, China — 6International Center for Quantum Materials, Beijing Institute of Technology, China — 7II. Physikalisches Institut, Universität zu Köln, Germany
The higher-order topological insulator α-Bi4Br4 is a promising, highly anisotropic quasi one-dimensional van der Waals material. Using a four-tip scanning tunneling microscope, we combine four-point resistance measurements in the square geometry on a bulk sample of α-Bi4Br4 with four-point resistance measurements on thin flakes in a linear configuration to disentangle the anisotropic resistivity tensor at room temperature (RT) and at 77 K: At RT, the resistivity along the chain direction is 6.4 times smaller than the resistivity perpendicular to the chains. At 77 K, this anisotropy reduces to 5.0. The vertical anisotropies are ∼ 1300 and ∼ 6500, at RT and 77 K, respectively.
Keywords: Topological Insulators; anisotropy; four-tip Scanning Tunneling Microscope; quasi one-dimensional crystals; van der Waals material