Spin accumulation and dynamics in inversion-symmetric van der Waals crystals

TL;DR

This study investigates spin-layer polarization in inversion-symmetric van der Waals crystals using time-resolved Kerr rotation, revealing temperature-dependent relaxation dynamics and the influence of magnetic fields, with implications for spintronic applications.

Contribution

It demonstrates the existence and dynamics of spin-layer polarization in inversion-symmetric WSe₂ and MoSe₂ crystals, providing experimental insights into their relaxation mechanisms.

Findings

Spin-layer relaxation in WSe₂ is phonon-limited at high temperatures.

Inter-layer hopping can be tuned by a small in-plane magnetic field.

MoSe₂ exhibits a shorter spin-layer lifetime consistent with stronger spin-orbit coupling.

Abstract

Inversion symmetric materials are forbidden to show an overall spin texture in their band structure in the presence of time-reversal symmetry. However, in van der Waals materials which lack inversion symmetry within a single layer, it has been proposed that a layer-dependent spin texture can arise leading to a coupled spin-layer degree of freedom. Here we use time-resolved Kerr rotation in inversion symmetric WSe$_{2}$ and MoSe$_{2}$ bulk crystals to study this spin-layer polarization and unveil its dynamics. Our measurements show that the spin-layer relaxation time in WSe$_2$ is limited by phonon-scattering at high temperatures and that the inter-layer hopping can be tunned by a small in-plane magnetic field at low temperatures, enhancing the relaxation rates. We find a significantly lower lifetime for MoSe$_{2}$ which agrees with theoretical expectations of a spin-layer polarization stabilized by the larger spin-orbit coupling in WSe$_2$.