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O: Fachverband Oberflächenphysik
O 4: Topology and Symmetry-Protected Materials
O 4.3: Talk
Monday, September 5, 2022, 11:00–11:15, H6
Lifting the Spin-Momentum Locking in Ultra-Thin Topological Insulator Films — Arthur Leis1, Jonathan Hofmann1, Michael Schleenvoigt2, Vasily Cherepanov1, Felix Lüpke1, Peter Schüffelgen2, Gregor Mussler2, Detlev Grützmacher2, •Bert Voigtländer1, and F. Stefan Tautz1 — 1Peter Grünberg Institut (PGI-3), Forschungszentrum Jülich, 52425 Jülich, Germany — 2Peter Grünberg Institut (PGI-9), Forschungszentrum Jülich, 52425 Jülich, Germany
3D topological insulators are known to carry 2D Dirac-like topological surface states in which spin-momentum locking prohibits backscattering. When thinned down to a few nanometers, the hybridization between the topological surface states at the top and bottom surfaces results in a topological quantum phase transition, which can lead to the emergence of a quantum spin Hall phase. Here, the thickness-dependent transport properties are studied on the example of BiSbTe3 films, with a four-tip scanning tunneling microscope. The findings reveal an exponential drop of the conductivity below the critical thickness. The steepness of this drop indicates the presence of spin-conserving backscattering between the top and bottom surface states, effectively lifting the spin-momentum locking and resulting in the opening of a gap at the Dirac point. Moreover, we probe the edge state conductance these films. The experiments provide a crucial step toward the detection of quantum spin Hall states in transport measurements.