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arXiv · 1308.5859

Evidence for topological band inversion of the phase change material Ge2Sb2Te5

Christian Pauly·Marcus Liebmann·Alessandro Giussani·Jens Kellner·Sven Just·Jaime Sánchez-Barriga·Emile Rienks·Oliver Rader·Raffaella Calarco·Gustav Bihlmayer·Markus Morgenstern
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Abstract

We present an angle-resolved photoemission study of a ternary phase change material, namely Ge2Sb2Te5, epitaxially grown on Si(111) in the metastable cubic phase. The observed upper bulk valence band shows a minimum at Gamma-bar being 0.3 eV below the Fermi level E_F and a circular Fermi contour around Gamma-bar with a dispersing diameter of 0.27-0.36 Anstroms^-1. This is in agreement with density functional theory calculations of the Petrov stacking sequence in the cubic phase which exhibits a topological surface state. The topologically trivial cubic KH stacking shows a valence band maximum at Gamma in line with all previous calculations of the hexagonal stable phase exhibiting the valence band maximum at Gamma for a trivial Z_2 topological invariant nu_0 and away from Gamma for non-trivial nu_0. Scanning tunneling spectroscopy exhibits a band gap of 0.4 eV around E_F.

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Christian Pauly, Marcus Liebmann, Alessandro Giussani, Jens Kellner, Sven Just, Jaime Sánchez-Barriga, Emile Rienks, Oliver Rader, Raffaella Calarco, Gustav Bihlmayer, Markus Morgenstern. 2013-11-28. Evidence for topological band inversion of the phase change material Ge2Sb2Te5. https://doi.org/10.1063/1.4847715

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