Exchange-enhanced spin-orbit splitting and its density dependence for electrons in monolayer transition metal dichalcogenides

TL;DR

This paper demonstrates that electron-electron interactions significantly enhance spin-orbit splitting in monolayer transition metal dichalcogenides, with a non-monotonic density dependence affecting spin relaxation and device performance.

Contribution

It reveals the exchange-enhancement of spin-orbit splitting in TMD monolayers and its critical density dependence, impacting spintronic applications.

Findings

Spin-orbit splitting is substantially enhanced by electron-electron interactions.

The enhancement peaks at a specific carrier density, $n_*$, affecting spin relaxation regimes.

Density dependence of SOS influences the performance of TMD-based spintronic devices.

Abstract

We show that spin-orbit splitting (SOS) in monolayers of semiconducting transition metal dichalcogenides (TMDs) is substantially enhanced by electron-electron interaction. This effect, similar to the exchange-enhancement of the electron g-factor, is most pronounced for conduction band electrons (in particular, in MoS$_2$), and it has a non-monotonic dependence on the carrier sheet density, $n$. That is, the SOS enhancement is peaked at the onset of filling of the higher-energy spin-split band by electrons, $n_*$, which also separates the regimes of slow (at $n<n_*$) and fast (for $n>n_*$) spin and valley relaxation of charge carriers. Moreover, this density itself is determined by the enhanced SOS value, making the account of exchange renormalisation important for the analysis of spintronic performance of field-effect transistors based on two-dimensional TMDs.