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

TLDR

Weyl fermions are massless chiral particles predicted by quantum field theory, yet unobserved as fundamental particles, and a Weyl semimetal realizes them as quasiparticles with surface Fermi arcs, offering a condensed‑matter platform for quantum‑field anomalies and topological classification beyond gapped insulators. The study identifies a topological Weyl semimetal state in transition‑metal monopnictide materials. First‑principles calculations on TaAs uncover bulk Weyl fermion cones and surface Fermi arcs. The calculations demonstrate that TaAs‑type materials host a Weyl semimetal state without requiring fine‑tuning of composition or magnetic order, enabling experimental realization of Weyl fermions and Fermi‑arc surface states.

Abstract

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.