Regensburg 2019 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 5: Topological insulators

HL 5.10: Talk

Monday, April 1, 2019, 12:00–12:15, H36

Early onset of a ‘−1’ quantized Hall plateau in HgMnTe / HgCdTe quantum wells close to charge neutrality — Saquib Shamim¹, •Wouter Beugeling¹, Jan Böttcher², Andreas Budewitz¹, Pragya Shekhar¹, Philipp Leubner¹, Hartmut Buhmann¹, Ewelina M. Hankiewicz², and Laurens W. Molenkamp¹ — ¹Physikalisches Institut (EP3), Würzburg University, Würzburg, Germany — ²Institut für Theoretische Physik und Astrophysik, Würzburg University, Würzburg, Germany

Transport measurements of HgCdTe/HgMnTe/HgCdTe quantum wells indicate that the Hall conductivity quantizes at −e²/h already for remarkably small magnetic fields of ∼ 100 mT and remains quantized up to a few tesla. This phenomenology is reminiscent of a suggestion [1] that the quantum anomalous Hall effect could occur in this material. However, the suggested mechanism of closing the bulk gap for one spin component does not apply to our setup due to insufficient magnetization at small magnetic fields.

Comparing our data to predictions obtained from k· p theory, we find that the particle-hole asymmetric dispersion gives rise to a Landau-level fan with a −e²/h plateau that spans a large range of magnetic field values. The Mn doping favours the onset at small magnetic fields due to the effect of the exchange coupling. We confirm our theory by showing that it remains consistent with experiments performed in a tilted magnetic field and at different temperatures.

[1] C.-X. Liu et al., Phys. Rev. Lett. 101, 146802 (2008).