Dresden 2014 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 42: Topological insulators (organized by O)

HL 42.9: Vortrag

Dienstag, 1. April 2014, 12:30–12:45, GER 38

Evidence for topological band inversion of the phase change material Ge2Sb2Te5 — •Marcus Liebmann1, Christian Pauly1, Alessandro Giussani2, Jens Kellner1, Sven Just1, Jaime Sanchez-Barriga3, Emile Rienks3, Oliver Rader3, Raffaella Calarco2, Gustav Bihlmayer4, and Markus Morgenstern11II. Inst. Phys. B, RWTH Aachen University — 2Paul-Drude-Institut für Festkörperelektronik, Berlin — 3Helmholtz-Zentrum für Materialien und Energie, BESSY, Berlin — 4Peter-Grünberg-Institut and Institute für Advanced Simulation, Forschungszentrum Jülich

We present an angle-resolved photoemission study of the ternary phase change material Ge2Sb2Te5, epitaxially grown on Si(111) in the metastable cubic phase. This material serves, e.g., in DVDs as a fast switchable material (1 ns) between the metallic cubic and an insulating amorphous phase. The observed upper bulk valence band shows a minimum at Γ being 0.3 eV below the Fermi level EF and a circular Fermi contour around Γ with a dispersing diameter of 0.27−0.36 Å−1. This is in agreement with density functional theory calculations of the Petrov stacking sequence of the cubic phase which is topologically non-trivial. Moreover, the results are in line with all previous calculations of Ge2Sb2Te5 exhibiting the valence band maximum at Γ for a trivial Z2 topology and away from Γ for a non-trivial one. Scanning tunneling spectroscopy exhibits a band gap of 0.4 eV around EF. Our finding opens the perspective of ns-switching between a topological crystalline and an insulating amorphous phase.

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