Signature of strong spin-orbital coupling in the large non-saturating magnetoresistance material WTe2

TL;DR

This study reveals a complex Fermi surface and strong spin-orbital coupling in WTe2, linking these electronic features to its large non-saturating magnetoresistance.

Contribution

The paper provides detailed electronic structure data and confirms strong spin-orbital coupling in WTe2 through both experimental and theoretical methods.

Findings

Complex Fermi surface with nine pockets identified

Circular dichroism indicates rich orbital angular momentum texture

Spin texture confirmed by density functional theory calculations

Abstract

We report the detailed electronic structure of WTe$_2$ by high resolution angle-resolved photoemission spectroscopy. Unlike the simple one electron plus one hole pocket type of Fermi surface topology reported before, we resolved a rather complicated Fermi surface of WTe$_2$. Specifically, there are totally nine Fermi pockets, including one hole pocket at the Brillouin zone center $\Gamma$, and two hole pockets and two electron pockets on each side of $\Gamma$ along the $\Gamma$-$X$ direction. Remarkably, we have observed circular dichroism in our photoemission spectra, which suggests that the orbital angular momentum exhibits a rich texture at various sections of the Fermi surface. As reported previously for topological insulators and Rashiba systems, such a circular dichroism is a signature for spin-orbital coupling (SOC). This is further confirmed by our density functional theory calculations, where the spin texture is qualitatively reproduced as the conjugate consequence of SOC. Since the backscattering processes are directly involved with the resistivity, our data suggest that the SOC and the related spin and orbital angular momentum textures may be considered in the understanding of the anomalous magnetoresistance of WTe$_2$.