# Interplay of valley polarization and dynamic nuclear polarization in 2D transition metal dichalcogenides

## TL;DR

This paper explores how hyperfine interactions in transition metal dichalcogenides lead to dynamic nuclear polarization, affecting spin-valley currents and excitonic properties, with implications for optical and transport phenomena.

## Contribution

It reveals a feedback mechanism where nuclear polarization influences valley polarization and proposes experimental detection methods.

## Key findings

- Hyperfine interactions induce significant nuclear polarization in TMDs.
- Nuclear polarization causes Zeeman shifts in excitonic transitions.
- Dynamic nuclear polarization saturates spin-valley polarization production.

## Abstract

The interplay of Ising spin-orbit coupling and non-trivial band topology in transition metal dichalcogenides (TMDs) produces anomalous transport and optical properties that are very different from a regular 2D electron gas. The spin-momentum locking of optically excited carriers near a valley point can give rise to an anomalous spin-valley Hall current under the application of an in-plane electric field. TMDs also exhibit strong electron-nuclear hyperfine interactions, but their effect on spin-valley-locked currents remains unknown. Here, we show that hyperfine interactions can create a feedback mechanism in which spin-valley currents generate significant dynamical nuclear polarization which in turn Zeeman shifts excitonic transitions out of resonance with an optical driving field, saturating the production of spin-valley polarization. We propose an experimental signature of dynamic nuclear polarization which can be detected via measurements of the anomalous Hall current. Our results help to elucidate the interplay of valley polarization and nuclear spin dynamics in TMDs.