Anisotropic ultrafast spin/valley dynamics in WTe2 films

TL;DR

This study reveals anisotropic ultrafast spin and valley dynamics in WTe2 films, demonstrating transient intra-valley transitions and polarization durations, with implications for high-speed spin/valleytronic devices.

Contribution

It uncovers the anisotropic ultrafast spin/valley dynamics in WTe2, highlighting intrinsic and extrinsic symmetry effects at room temperature.

Findings

Transient intra-valley transition (~0.8 ps)

Polarization duration (~5 ps)

Six-fold and two-fold symmetry anisotropy

Abstract

WTe2 Weyl semimetal hosts the natural broken inversion symmetry and strong spin orbit coupling, making it promising for exotic spin/valley dynamics within a picosecond timescale. Here, we unveil an anisotropic ultrafast spin/valley dynamics in centimeter-scale, single-crystalline Td-WTe2 films using a femtosecond pump-probe technique at room temperature. We observe a transient (~0.8 ps) intra-valley transition and a subsequent polarization duration (~5 ps) during the whole spin/valley relaxation process. Furthermore, the relaxation exhibits the remarkable anisotropy of approximately six-fold and two-fold symmetries due to the intrinsic anisotropy along the crystalline orientation and the extrinsic matrix element effect, respectively. Our results offer a prospect for the ultrafast manipulation of spin/valleytronics in topological quantum materials for dissipationless high-speed spin/valleytronic devices.