Anisotropic three-dimensional quantum Hall effect and magnetotransport in mesoscopic Weyl semimetals

TL;DR

This paper uncovers a unique three-dimensional anisotropic quantum Hall effect in Weyl semimetals, revealing unconventional transport phenomena and challenging traditional bulk-boundary correspondence theories.

Contribution

It demonstrates the existence of a fully three-dimensional anisotropic quantum Hall effect in Weyl semimetals, highlighting novel transport behaviors and the absence of conventional bulk-boundary correspondence.

Findings

Suppression of QHE when current is aligned with the Weyl point axis.

Reversal of magnetoresistance from negative to positive along magnetic field.

Unconventional anisotropic quantum transport phenomena observed.

Abstract

Weyl semimetals are emerging to become a new class of quantum-material platform for various novel phenomena. Especially, the Weyl orbit made from surface Fermi arcs and bulk relativistic states is expected to play a key role in magnetotransport, leading even to a three-dimensional quantum Hall effect (QHE). It is experimentally and theoretically important although yet unclear whether it bears essentially the same phenomenon as the conventional two-dimensional QHE. We discover an unconventional fully three-dimensional anisotropy in the quantum transport under magnetic field. Strong suppression and even disappearance of QHE occur when Hall-bar current is rotated away from being transverse to parallel with respect to the Weyl point alignment, which is attributed to a peculiar absence of conventional bulk-boundary correspondence. Besides, transport along the magnetic field can exhibit a remarkable reversal from negative to positive magnetoresistance. These results establish the uniqueness of this QHE system as a novel three-dimensional quantum matter.