Quantum Hall effect induced by chiral Landau levels in topological semimetal films

TL;DR

This paper theoretically investigates the quantum Hall effect in topological semimetal films, revealing how confinement and chiral Landau levels lead to quantized conductance and anisotropic states, with implications for Weyl and Dirac semimetals.

Contribution

It provides a new theoretical framework for understanding quantum Hall states in topological semimetal films considering confinement effects and chiral Landau levels.

Findings

Quantized Hall conductance arises from bulk subbands due to chiral Landau levels.

Quantum Hall state exhibits strong anisotropy depending on confinement direction.

Confined Dirac semimetals can host both quantum Hall and quantum spin Hall states.

Abstract

Motivated by recent transport experiments, we theoretically study the quantum Hall effect in topological semimetal films. Owing to the confinement effect, the bulk subbands originating from the chiral Landau levels establish energy gaps that have quantized Hall conductance and can be observed in relatively thick films. We find that the quantum Hall state is strongly anisotropic for different confinement directions not only due to the presence of the surface states but also because of the bulk chiral Landau levels. As a result, we re-examine the quantum Hall effect from the surface Fermi arcs and chiral modes in Weyl semimetals and give a more general view into this problem. Besides, we also find that when a topological Dirac semimetal is confined in its rotational symmetry axis, it hosts both quantum Hall and quantum spin Hall states, in which the helical edge states are protected by the conservation of the spin-$z$ component.