Dimensionality-dependent type-II Weyl semimetal state in Mo$_{0.25}$W$_{0.75}$Te$_{2}$

TL;DR

This study demonstrates the dimensionality-dependent transport properties of Mo$_{0.25}$W$_{0.75}$Te$_{2}$, confirming its nature as a type-II Weyl semimetal through experimental evidence and theoretical analysis.

Contribution

The paper introduces a novel in situ dimensionality-tuning method to identify type-II Weyl semimetals, revealing unique transport phenomena linked to the material's band structure.

Findings

Observation of chiral-anomaly-induced anisotropic magneto-conductivity

Detection of thickness-dependent quantum oscillations

Theoretical explanation of quantum oscillations as Weyl-orbit-like phenomena

Abstract

Weyl nodes and Fermi arcs in type-II Weyl semimetals (WSMs) have led to lots of exotic transport phenomena. Recently, Mo$_{0.25}$W$_{0.75}$Te$_{2}$ has been established as a type-II WSM with Weyl points located near Fermi level, which offers an opportunity to study its intriguing band structure by electrical transport measurements. Here, by selecting a special sample with the thickness gradient across two- (2D) and three-dimensional (3D) regime, we show strong evidences that Mo$_{0.25}$W$_{0.75}$Te$_{2}$ is a type-II Weyl semimetal by observing the following two dimensionality-dependent transport features: 1) A chiral-anomaly-induced anisotropic magneto-conductivity enhancement, proportional to the square of in-plane magnetic field (B$_{in}$$^{2}$); 2) An additional quantum oscillation with thickness-dependent phase shift. Our theoretical calculations show that the observed quantum oscillation originates from a Weyl-orbit-like scenario due to the unique band structure of Mo$_{0.25}$W$_{0.75}$Te$_{2}$. The in situ dimensionality-tuned transport experiment offers a new strategy to search for type-II WSMs.