Interplay of Valley, Orbital, Spin, and Layer Degrees of Freedom in Ta$_2$CS$_2$ MXene

TL;DR

This paper explores how the noncentrosymmetric MXene Ta$_2$CS$_2$ hosts and controls multiple coupled degrees of freedom, leading to tunable spin and orbital phenomena relevant for advanced spintronic applications.

Contribution

It reveals the interplay of valley, spin, orbital, and layer degrees of freedom in Ta$_2$CS$_2$, and demonstrates their tunability via electric polarization and spin-orbit interactions.

Findings

Valley-orbital and orbital-layer couplings are identified in Ta$_2$CS$_2$.

Electric polarization enables control over spin and orbital textures.

Orbital and spin Hall effects are observed due to these coupled degrees of freedom.

Abstract

We show that the MXene Ta$_2$CS$_2$ provides an excellent platform for hosting multiple coupled degrees of freedom, viz., valley, spin, orbital, and layer. The interplay among these degrees of freedom gives rise to a range of intriguing properties in reciprocal space, including valley-orbital and orbital-layer coupling. In the presence of spin-orbit interaction, these couplings lead to valley-dependent and layer-dependent spin splitting of the electronic bands. We further show that the intrinsic electric polarization in Ta$_2$CS$_2$ introduces an additional tuning parameter, enabling control over these coupled degrees of freedom and resulting in switchable valley-dependent orbital moments and Zeeman-like spin splitting. We demonstrate that these nontrivial orbital and spin textures manifest in the orbital and spin Hall effects, respectively. Our results establish noncentrosymmetric MXenes as a promising platform for exploring the interplay among multiple degrees of freedom, their tunability, and the resulting orbital and spin transport phenomena in these two-dimensional materials, thereby paving the way for next-generation spin-orbitronic devices.