Regensburg 2019 – wissenschaftliches Programm
HL 5.10: Vortrag
Montag, 1. April 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  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.
 C.-X. Liu et al., Phys. Rev. Lett. 101, 146802 (2008).