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Phase change alloys are used for non-volatile random-access memories exploiting the conductivity contrast between amorphous and metastable, crystalline phase. However, this contrast has never been directly related to the electronic band structure. Here we employ photoelectron spectroscopy to map the relevant bands for metastable, epitaxial GeSbTe films. The constant energy surfaces of the valence band close to the Fermi level are hexagonal tubes with little dispersion perpendicular to the (111) surface. The electron density responsible for transport belongs to the tails of this bulk valence band, which is broadened by disorder, ie, the Fermi level is 100 meV above the valence band maximum. This result is consistent with transport data of such films in terms of charge carrier density and scattering time. In addition, we find a state in the bulk band gap with linear dispersion, which might be of topological origin.
Nature Publishing Group
Publication date: 
22 Feb 2018

Jens Kellner, Gustav Bihlmayer, Marcus Liebmann, Sebastian Otto, Christian Pauly, Jos Emiel Boschker, Valeria Bragaglia, Stefano Cecchi, Rui Ning Wang, Volker L Deringer, Philipp Küppers, Priyamvada Bhaskar, Evangelos Golias, Jaime Sánchez-Barriga, Richard Dronskowski, Thomas Fauster, Oliver Rader, Raffaella Calarco, Markus Morgenstern

Biblio References: 
Volume: 1 Issue: 1 Pages: 1-11
Communications Physics