Photo-induced anomalous Hall effect in the type-II Weyl-semimetal WTe2 at room-temperature

TL;DR

This study demonstrates room-temperature photo-induced anomalous Hall effect in WTe2, driven by Berry curvature and long-lived spin states, revealing potential for optospintronics in layered materials.

Contribution

It reports the first observation of a photo-induced anomalous Hall effect in WTe2 at room temperature, linking it to Berry curvature and spin lifetime effects.

Findings

Anomalous Hall voltage is induced by circularly polarized light.

The effect aligns with a specific crystal axis.

Decay time exceeds electron-phonon scattering time.

Abstract

Using Hall photovoltage measurements, we demonstrate that an anomalous Hall-voltage can be induced in few layer WTe2 under circularly polarized light illumination. By applying a bias voltage along different crystal axes, we find that the photo-induced anomalous Hall conductivity coincides with a particular crystal axis. Our results are consistent with the underlying Berry-curvature exhibiting a dipolar distribution due to the breaking of crystal inversion symmetry. Using a time-resolved optoelectronic auto-correlation spectroscopy, we find that the decay time of the anomalous Hall voltage exceeds the electron-phonon scattering time by orders of magnitude but is consistent with the comparatively long spin-lifetime of carriers in the momentum-indirect electron and hole pockets in WTe2. Our observation suggests, that a helical modulation of an otherwise isotropic spin-current is the underlying mechanism of the anomalous Hall effect.