ORIGIN OF THE QUASI-QUANTIZED HALL EFFECT IN ZrTe₅

Stanislaw Galeski, MPI CPfS Dresden and Sergei Zherlitsyn, HLD Dresden.

The quantum Hall effect (QHE) is traditionally considered to be a purely two-dimensional (2D) phenomenon. Recently, however, a three-dimensional (3D) version of the QHE was reported in the Dirac semimetal ZrTe₅. Researchers from Germany, USA, and Sweden have now succeeded in identifying the mechanism behind the quasiquantization of the Hall effect (qQHE). A direct comparison of the experimental data with linear-response calculations based on an effective 3D Dirac Hamiltonian of ZrTe₅ suggests that the quasi-quantization of the observed Hall response emerges from the interplay of low charge-carrier density and the Dirac character of the charge carriers. From previous charge-transport experiments, the 3D QHE was hypothetically proposed to arise from a magnetic-field-driven Fermi-surface instability with gapping of the Fermi surface and appearing of charge-density waves (CDW) in the quantum limit of ZrTe₅. In our comprehensive study, we combined magnetization, ultrasound, magneto-transport, scanning-tunneling, and Raman spectroscopy experiments with advanced high-magnetic-field generation. Our investigations show no signatures of a Fermi-surface instability. Our results indicate that the state underlying the emergence of Hall plateaus in the quantum limit of ZrTe₅ is, in fact, gapless and exhibits the behavior of a Fermi sea of a Landau-quantized 3D Dirac semimetal. Our findings establish the Hall effect in ZrTe₅ as a truly threedimensional relative of the quantum Hall effect in 2D systems, and a prime candidate for the observation of relativistic chiral surface states.

Figure: Longitudinal electrical resistivity at 2 K as a function of magnetic field B applied along the b axis of the crystal (a) up to ±70 T and (b) up to ±20 T. (c) Low-field longitudinal and transversal Hall resistivity revealing a quasi-quantized Hall effect in ZrTe₅. (d) Comparison between measured and calculated sound velocity in ZrTe₅.

Origin of the quasi-quantized Hall effect in ZrTe₅, S. Galeski, T. Ehmcke, R. Wawrzyńczak, P. M. Lozano, K. Cho, A. Sharma, S. Das, F. Küster, P. Sessi, M. Brando, R. Küchler, A. Markou, M. König, P. Swekis, C. Felser, Y. Sassa, Q. Li, G. Gu, M. v. Zimmermann, O. Ivashko, D. I. Gorbunov, S. Zherlitsyn, T. Förster, S. S. P. Parkin, J. Wosnitza, T. Meng, and J. Gooth, Nat. Commun. 12, 3197 (2021).

https://www.nature.com/articles/s41467-021-23435-y

Contact: Stanislaw.Galeski@cpfs.mpg.de