A Weyl Fermion semimetal with surface Fermi arcs in the transition metal monopnictide TaAs class.

Shin-Ming Huang,Nasser Alidoust,Chenglong Zhang,Guoqing Chang,Madhab Neupane,Hsin Lin,Shuang Jia,Chi-Cheng Lee,Su-Yang Xu,M Zahid Hasan,Ilya Belopolski,Guang Bian,Baokai Wang,Arun Bansil

doi:10.1038/ncomms8373

Abstract

Weyl fermions are massless chiral fermions that play an important role in quantum field theory but have never been observed as fundamental particles. A Weyl semimetal is an unusual crystal that hosts Weyl fermions as quasiparticle excitations and features Fermi arcs on its surface. Such a semimetal not only provides a condensed matter realization of the anomalies in quantum field theories but also demonstrates the topological classification beyond the gapped topological insulators. Here, we identify a topological Weyl semimetal state in the transition metal monopnictide materials class. Our first-principles calculations on TaAs reveal its bulk Weyl fermion cones and surface Fermi arcs. Our results show that in the TaAs-type materials the Weyl semimetal state does not depend on fine-tuning of chemical composition or magnetic order, which opens the door for the experimental realization of Weyl semimetals and Fermi arc surface states in real materials.

Highlights

Weyl fermions are massless chiral fermions that play an important role in quantum field theory but have never been observed as fundamental particles
We have grown single crystals of TaAs where the crystal structure is consistent with previous reports[28]. We believe that this material is the platform for the experimental realization of the long-sought-for Weyl fermion semimetal phase and Fermi arc surface states
In order to find a Weyl semimetal that respects time-reversal symmetry, one needs to search for materials that break space inversion symmetry

Summary

Introduction

Weyl fermions are massless chiral fermions that play an important role in quantum field theory but have never been observed as fundamental particles. Unlike the two-dimensional (2D) Dirac cones in graphene[9], the 3D Dirac cones in spin–orbit materials[15,16] or the 2D Dirac cone surface states of Bi2Se3(refs 10,11), the degeneracy associated with a Weyl point depends only on the translation symmetry of the crystal lattice This makes the unique properties associated with this electron band structure more robust. We have grown single crystals of TaAs where the crystal structure is consistent with previous reports[28] We believe that this material is the platform for the experimental realization of the long-sought-for Weyl fermion semimetal phase and Fermi arc surface states

Methods

Results

Conclusion