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

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.

6 pages, 4 figures

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• Maximizing the thermoelectric performance of topological insulator Bi2Te3 films in the few-quintuple layer regime
• Exchange interaction and its tuning in magnetic binary chalcogenides
• Spin- and angle-resolved photoemission on topological materials
• Realization of bulk insulating property and carrier manipulation in reversible spin current regime of the ideal topological insulator TlBiSe2
• Multiple superconducting phases driven by pressure in the topological insulator GeSb4Te7
• Pressure-driven superconductivity in the topological insulator GeBi4Te7