Spin polarization and texture of the Fermi arcs in the Weyl Fermion semimetal TaAs

TL;DR

This study experimentally measures the spin polarization and texture of Fermi arcs in the Weyl semimetal TaAs, revealing high spin polarization and in-plane spin texture, which are significant for understanding topological properties and potential spintronic applications.

Contribution

First experimental measurement of Fermi arc spin polarization in TaAs, showing high polarization and in-plane texture, clarifying topological features of Weyl semimetals.

Findings

Fermi arcs exhibit up to 80% spin polarization.

Spin texture is completely in-plane.

Chirality of Weyl nodes cannot be deduced from Fermi arc spin texture.

Abstract

A Weyl semimetal is a new state of matter that host Weyl fermions as quasiparticle excitations. The Weyl fermions at zero energy correspond to points of bulk band degeneracy, Weyl nodes, which are separated in momentum space and are connected only through the crystal's boundary by an exotic Fermi arc surface state. We experimentally measure the spin polarization of the Fermi arcs in the first experimentally discovered Weyl semimetal TaAs. Our spin data, for the first time, reveal that the Fermi arcs' spin polarization magnitude is as large as 80% and possesses a spin texture that is completely in-plane. Moreover, we demonstrate that the chirality of the Weyl nodes in TaAs cannot be inferred by the spin texture of the Fermi arcs. The observed non-degenerate property of the Fermi arcs is important for the establishment of its exact topological nature, which reveal that spins on the arc form a novel type of 2D matter. Additionally, the nearly full spin polarization we observed (~80%) may be useful in spintronic applications.