Unconventional charge-spin conversion in Weyl-semimetal WTe2

TL;DR

This paper reports an unconventional charge-to-spin conversion in WTe2, a Weyl semimetal, enabled by its unique symmetry and spin Berry curvature, demonstrating efficient room-temperature spin injection and detection in graphene for spintronic applications.

Contribution

It reveals a novel charge-to-spin conversion mechanism in WTe2 driven by its reduced symmetry and spin Berry curvature, expanding the understanding of spin generation in topological materials.

Findings

Unconventional charge-to-spin conversion observed in WTe2.

Efficient spin injection and detection in graphene at room temperature.

Potential for WTe2 in non-magnetic spintronic devices.

Abstract

An outstanding feature of topological quantum materials is their novel spin topology in the electronic band structures with an expected large charge-to-spin conversion efficiency. Here, we report a charge current-induced spin polarization in the type-II Weyl semimetal candidate WTe2 and efficient spin injection and detection in a graphene channel up to room temperature. Contrary to the conventional spin Hall and Rashba-Edelstein effects, our measurements indicate an unconventional charge-to-spin conversion in WTe2, which is primarily forbidden by the crystal symmetry of the system. Such a large spin polarization can be possible in WTe2 due to a reduced crystal symmetry combined with its large spin Berry curvature, spin-orbit interaction with a novel spin-texture of the Fermi states. We demonstrate a robust and practical method for electrical creation and detection of such a spin polarization using both charge-to-spin conversion and its inverse phenomenon and utilized it for efficient spin injection and detection in a graphene channel up to room temperature. These findings open opportunities for utilizing topological Weyl materials as non-magnetic spin sources in allelectrical van der Waals spintronic circuits and for low-power and high-performance non-volatile spintronic technologies.