Experimental discovery of Weyl semimetal TaAs

TL;DR

This paper reports the first experimental observation of a Weyl semimetal in TaAs, confirming its exotic electronic properties through surface state measurements and theoretical calculations.

Contribution

It provides the first experimental evidence of a Weyl semimetal, demonstrating Fermi arcs and confirming theoretical predictions for TaAs.

Findings

Observation of Fermi arcs on TaAs surface

First-principles calculations match experimental data

Confirmation of TaAs as a Weyl semimetal

Abstract

Weyl semimetals are a class of materials that can be regarded as three-dimensional analogs of graphene breaking time reversal or inversion symmetry. Electrons in a Weyl semimetal behave as Weyl fermions, which have many exotic properties, such as chiral anomaly and magnetic monopoles in the crystal momentum space. The surface state of a Weyl semimetal displays pairs of entangled Fermi arcs at two opposite surfaces. However, the existence of Weyl semimetals has not yet been proved experimentally. Here we report the experimental realization of a Weyl semimetal in TaAs by observing Fermi arcs formed by its surface states using angle-resolved photoemission spectroscopy. Our first-principles calculations, matching remarkably well with the experimental results, further confirm that TaAs is a Weyl semimetal.