Prediction of an arc-tunable Weyl Fermion metallic state in Mo(x)W(1-x)Te2.

Tay-Rong Chang,Horng-Tay Jeng,Daniel S Sanchez,M Zahid Hasan,Hsin Lin,Baokai Wang,Chi-Cheng Lee,Arun Bansil,Guang Bian,Shin-Ming Huang,Hao Zheng,Su-Yang Xu,Ilya Belopolski,Nasser Alidoust,Madhab Neupane,Guoqing Chang

doi:10.1038/ncomms10639

Abstract

A Weyl semimetal is a new state of matter that hosts Weyl fermions as emergent quasiparticles. The Weyl fermions correspond to isolated points of bulk band degeneracy, Weyl nodes, which are connected only through the crystal's boundary by exotic Fermi arcs. The length of the Fermi arc gives a measure of the topological strength, because the only way to destroy the Weyl nodes is to annihilate them in pairs in the reciprocal space. To date, Weyl semimetals are only realized in the TaAs class. Here, we propose a tunable Weyl state in MoxW1−xTe2 where Weyl nodes are formed by touching points between metallic pockets. We show that the Fermi arc length can be changed as a function of Mo concentration, thus tuning the topological strength. Our results provide an experimentally feasible route to realizing Weyl physics in the layered compound MoxW1−xTe2, where non-saturating magneto-resistance and pressure-driven superconductivity have been observed.

Highlights

A Weyl semimetal is a new state of matter that hosts Weyl fermions as emergent quasiparticles
The band structure degeneracies in Weyl semimetals are uniquely robust against disorder[6,8,17], in contrast to the Dirac nodes in graphene, topological insulators and Dirac semimetals, which depend on additional symmetries beyond the translational symmetry[13,14,15,16,17,18]
Within a moderate doping regime, the momentum space distance between the Weyl nodes and the length of the Fermi arcs can be continuously tuned from 0 to B3% of the Brillouin zone (BZ) size via changing Mo concentration, increasing the topological strength of the system

Summary

Introduction

A Weyl semimetal is a new state of matter that hosts Weyl fermions as emergent quasiparticles. Our calculation (Fig. 3a) clearly shows the topological Fermi arc surface state, which connects the direct pair of Weyl nodes.

Results

Conclusion