Geometry-induced spin-filtering in photoemission maps from WTe$_2$ surface states

TL;DR

This paper reveals a geometry-induced spin-filtering effect in WTe$_2$ surface states, caused by low symmetry, leading to asymmetric spin textures in photoemission that are not present in the initial states.

Contribution

It introduces a new spin-filtering phenomenon in WTe$_2$ surface states driven by geometric symmetry breaking, supported by experimental and theoretical analysis.

Findings

Observation of asymmetric spin textures in photoemission maps

Reproduction of effects through theoretical modeling

Identification of time-reversal symmetry breaking in photoemission

Abstract

We demonstrate that an important quantum material WTe$_2$ exhibits a new type of geometry-induced spin-filtering effect in photoemission, stemming from low symmetry that is responsible for its exotic transport properties. Through the laser-driven spin-polarized angle-resolved photoemission Fermi surface mapping, we showcase highly asymmetric spin textures of electrons photoemitted from the surface states of WTe$_2$. Such asymmetries are not present in the initial state spin textures, which are bound by the time-reversal and crystal lattice mirror plane symmetries. The findings are reproduced qualitatively by theoretical modeling within the one-step model photoemission formalism. The effect could be understood within the free-electron final state model as an interference due to emission from different atomic sites. The observed effect is a manifestation of time-reversal symmetry breaking of the initial state in the photoemission process, and as such it cannot be eliminated, but only its magnitude influenced, by special experimental geometries.