Parts | Days | Selection | Search | Updates | Downloads | Help
TT: Fachverband Tiefe Temperaturen
TT 15: Quantum Transport and Quantum Hall Effects I (joint session HL/TT)
TT 15.7: Talk
Monday, March 27, 2023, 17:00–17:15, JAN 0027
Massive and topological surface states in strained HgTe and evidence for parity anomaly — •Wouter Beugeling1,2, Lixian Wang1,2, David M. Mahler1,2, Valentin L. Müller1,2, Ewelina M. Hankiewicz3, Hartmut Buhmann1,2, and Laurens W. Molenkamp1,2 — 1Institute for Topological Insulators, Würzburg, Germany — 2Physikalisches Institut (EP III), Würzburg University, Würzburg, Germany — 3Institute for Theoretical Physics and Astrophysics (TP IV), Würzburg University, Würzburg, Germany
The idea that band inversion in a narrow-gap material can lead to Dirac-type surface states was noted by Volkov and Pankratov in the 1980’s. Only about two decades later, it was realized that the surface states of topological insulators are the gapless Dirac states predicted by them. The massive Volkov-Pankratov states received much less attention. They are pulled from the bulk in a sufficiently large electric field and are topologically trivial. Until recently, direct evidence in the form of transport measurements was elusive.
From our magneto-transport experiments on a three-dimensional topological insulator heterostructure (strained HgTe), we demonstrate the coexistence of massless and massive Volkov-Pankratov states. The well-developed Hall quantization in the n- and the p-type regime is due to the topological surface state and the massive Volkov-Pankratov states, respectively, as confirmed by k·p theory. In a second series of experiments, we find a remarkable re-entrant quantum Hall effect in the p-type regime, which we can trace to spectral asymmetry, a salient manifestation of parity anomaly in a solid-state system.