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@ARTICLE{Leis:1041583,
      author       = {Leis, Arthur and Schleenvoigt, Michael and Cherepanov,
                      Vasily and Lüpke, Felix and Schüffelgen, Peter and
                      Mussler, Gregor and Grützmacher, Detlev and Voigtländer,
                      Bert and Tautz, F. Stefan},
      title        = {{L}ifting the spin-momentum locking in ultra-thin
                      topological insulator films},
      publisher    = {arXiv},
      reportid     = {FZJ-2025-02322},
      year         = {2021},
      abstract     = {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.},
      keywords     = {Mesoscale and Nanoscale Physics (cond-mat.mes-hall) (Other)
                      / FOS: Physical sciences (Other)},
      cin          = {PGI-3 / PGI-9},
      cid          = {I:(DE-Juel1)PGI-3-20110106 / I:(DE-Juel1)PGI-9-20110106},
      pnm          = {5213 - Quantum Nanoscience (POF4-521)},
      pid          = {G:(DE-HGF)POF4-5213},
      typ          = {PUB:(DE-HGF)25},
      doi          = {10.48550/ARXIV.2106.06217},
      url          = {https://juser.fz-juelich.de/record/1041583},
}