Two Types of 3D Quantum Hall Effects in Multilayer WTe$_2$

TL;DR

This paper reports the observation of two distinct types of three-dimensional quantum Hall effects in multilayer WTe2, arising from bulk and surface states, revealing new transport phenomena in topological semimetals.

Contribution

It demonstrates the coexistence and crossover of bulk and surface quantum Hall effects in multilayer WTe2, highlighting two novel types of 3D QHE driven by magnetic field.

Findings

Observation of 3D QHE from bulk states at low magnetic fields.

Detection of 3D QHE from Weyl orbits at high magnetic fields.

Crossover between bulk and surface quantized transport.

Abstract

Interplay between the topological surface states and bulk states gives rise to diverse exotic transport phenomena in topological materials. The recently proposed Weyl orbit in topological semimetals in the presence of magnetic field is a remarkable example. This novel closed magnetic orbit consists of Fermi arcs on two spatially separated sample surfaces which are connected by the bulk chiral zero mode, which can contribute to transport. Here we report Shubnikov-de Haas (SdH) oscillation and its evolution into quantum Hall effect (QHE) in multilayered type-II Weyl semimetal WTe2. We observe both the three-dimensional (3D) QHE from bulk states by parallelly stacking of confined two-dimensional layers in the low magnetic field region and the 3D QHE in the quantized surface transport due to Weyl orbits in the high magnetic field region. Our study of the two types of novel QHEs controlled by magnetic field and our demonstration of the crossover between quantized bulk and surface transport provide an essential platform for the future quantized transport studies in topological semimetals.