Topologically Nontrivial Phase-Change Compound GeSb<sub>2</sub>Te<sub>4</sub>.

Nurmamat, Munisa; Okamoto, Kazuaki; Zhu, Siyuan; Menshchikova, Tatiana V; Rusinov, Igor P; Korostelev, Vladislav O; Miyamoto, Koji; Okuda, Taichi et al. · ACS Nano · 2020

basic_science · Level V

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Abstract

Chalcogenide phase-change materials show strikingly contrasting optical and electrical properties, which has led to their extensive implementation in various memory devices. By performing spin-, time-, and angle-resolved photoemission spectroscopy combined with the first-principles calculation, we report the experimental results that the crystalline phase of GeSb<sub>2</sub>Te<sub>4</sub> is topologically nontrivial in the vicinity of the Dirac semimetal phase. The resulting linearly dispersive bulk Dirac-like bands that cross the Fermi level and are thus responsible for conductivity in the stable crystalline phase of GeSb<sub>2</sub>Te<sub>4</sub> can be viewed as a 3D analogue of graphene. Our finding provides us with the possibility of realizing inertia-free Dirac currents in phase-change materials.