Observation of Weyl nodes and Fermi arcs in TaP

TL;DR

This paper reports the experimental observation of Weyl nodes and Fermi arcs in TaP, establishing it as a simple Weyl semimetal with potential for fundamental research and applications.

Contribution

It demonstrates that TaP hosts only a single type of Weyl fermions, unlike TaAs, using combined ARPES and first-principles calculations.

Findings

Weyl nodes are observed near the chemical potential.

Fermi arcs are detected on the Ta-terminated surface.

TaP hosts only one type of Weyl fermions, unlike TaAs.

Abstract

A Weyl semimetal possesses spin-polarized band-crossings, called Weyl nodes, connected by topological surface arcs. The low-energy excitations near the crossing points behave the same as massless Weyl fermions, leading to exotic properties like chiral anomaly. To have the transport properties dominated by Weyl fermions, Weyl nodes need to locate nearly at the chemical potential and enclosed by pairs of individual Fermi surfaces with nonzero Fermi Chern numbers. Combining angle-resolved photoemission spectroscopy and first-principles calculation, here we show that TaP is a Weyl semimetal with only single type of Weyl fermions, topologically distinguished from TaAs where two types of Weyl fermions contribute to the low-energy physical properties. The simple Weyl fermions in TaP are not only of fundamental interests but also of great potential for future applications. Fermi arcs on the Ta-terminated surface are observed, which appear in a different pattern from that on the As-termination in TaAs and NbAs.