Dresden 2017 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 70: Topological Insulators I (joined session with TT)

HL 70.8: Vortrag

Donnerstag, 23. März 2017, 12:00–12:15, POT 251

Observation of the Quantum Anomalous Hall Effect depending on structural properties of (VBiSb)₂Te₃ layers — •Martin Winnerlein, Steffen Schreyeck, Stefan Grauer, Sabine Rosenberger, Kajetan Fijalkowski, Charles Gould, Karl Brunner, and Laurens W. Molenkamp — Physikalisches Institut, Experimentelle Physik III, Universität Würzburg, Am Hubland, D-97074 Würzburg, Germany

The quantum anomalous Hall effect is observed in thin V-doped (BiSb)₂Te₃ layers, a magnetic topological insulator. Thin layers revealing quantization are reproducibly deposited by molecular beam epitaxy at growth conditions effecting a compromise between controlled layer properties and high crystal quality. The influence of Sb content, layer thickness, structural quality, used substrates and cap layers is studied.

The Sb content is the main layer parameter to be optimized in order to approach charge neutrality. The Sb content is reliably determined from the in-plane lattice constant measured by X-ray diffraction even in thin layers. Within a narrow range at about 80% Sb content, the Hall resistivity reveals a maximum at 4 K and quantizes at mK temperatures [1]. Under these conditions thin layers grown on Si(111) or InP(111) and with or without a Te cap layer exhibit quantization. The quantization persists independently from the substrate, cap layer, the limited crystal quality and the degradation of the layer. This proves the robustness of the quantum anomalous Hall effect.

[1] S. Grauer et al., Phys. Rev. B 92, 201304 (2015).