%0 Electronic Article
%A Leis, Arthur
%A Schleenvoigt, Michael
%A Cherepanov, Vasily
%A Lüpke, Felix
%A Schüffelgen, Peter
%A Mussler, Gregor
%A Grützmacher, Detlev
%A Voigtländer, Bert
%A Tautz, F. Stefan
%T Lifting the spin-momentum locking in ultra-thin topological insulator films
%I arXiv
%M FZJ-2025-02322
%D 2021
%X Three-dimensional (3D) topological insulators (TIs) 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, we study the thickness-dependent transport properties across the quantum phase transition on the example of (Bi$_{0.16}$Sb$_{0.84}$)$_2$Te$_3$ films, with a four-tip scanning tunnelling microscope. Our 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. Our experiments provide crucial steps towards the detection of quantum spin Hall states in transport measurements.
%K Mesoscale and Nanoscale Physics (cond-mat.mes-hall) (Other)
%K FOS: Physical sciences (Other)
%F PUB:(DE-HGF)25
%9 Preprint
%R 10.48550/ARXIV.2106.06217
%U https://juser.fz-juelich.de/record/1041583