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arXiv · 1304.7648

Separating the bulk and surface n- to p-type transition in the topological insulator GeBi(4-x)SbxTe7

Stefan Muff·Fabian von Rohr·Gabriel Landolt·Bartosz Slomski·Andreas Schilling·Robert J. Cava·Jürg Osterwalder·J. Hugo Dil
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Abstract

We identify the multi-layered compound GeBi4Te7 to be a topological insulator with a freestanding Dirac point, slightly above the valence band maximum, using angle-resolved photoemission spectroscopy (ARPES) measurements. The spin polarization satisffies the time reversal symmetry of the surface states, visible in spin-resolved ARPES. For increasing Sb content in GeBi(4-x)SbxTe7 we observe a transition from n- to p-type in bulk sensitive Seebeck coefficient measurements at a doping of x = 0.6. In surface sensitive ARPES measurements a rigid band shift is observed with Sb doping, accompanied by a movement of the Dirac point towards the Fermi level. Between x = 0.8 and x = 1 the Fermi level crosses the band gap, changing the surface transport regime. This difference of the n- to p-type transition between the surface region and the bulk is caused by band bending effects which are also responsible for a non-coexistence of insulating phases in the bulk and in the near surface region.

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Stefan Muff, Fabian von Rohr, Gabriel Landolt, Bartosz Slomski, Andreas Schilling, Robert J. Cava, Jürg Osterwalder, J. Hugo Dil. 2013-11-15. Separating the bulk and surface n- to p-type transition in the topological insulator GeBi(4-x)SbxTe7. https://doi.org/10.1103/physrevb.88.035407

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