# Magnetic field induced polarization enhancement in monolayers of tungsten dichalcogenides: Effects of temperature

## TL;DR

This study demonstrates that applying low magnetic fields enhances optical polarization in monolayer tungsten dichalcogenides, with temperature-dependent effects linked to exciton dynamics and material-specific relaxation processes.

## Contribution

It provides new insights into magnetic field effects on exciton polarization and valley pseudospin relaxation in monolayer WS2 and WSe2, using a rate equation model.

## Key findings

- Magnetic fields as low as 20 mT significantly enhance exciton polarization.
- Temperature influences the polarization degree and relaxation dynamics.
- Differences in dark exciton relaxation between WS2 and WSe2 are characterized.

## Abstract

Optical orientation of localized/bound excitons is shown to be effectively enhanced by the application of magnetic fields as low as 20 mT in monolayer WS$_2$. At low temperatures, the evolution of the polarization degree of different emission lines of monolayer WS$_2$ with increasing magnetic fields is analyzed and compared to similar results obtained on a WSe$_2$ monolayer. We study the temperature dependence of this effect up to $T=60$ K for both materials, focusing on the dynamics of the valley pseudospin relaxation. A rate equation model is used to analyze our data and from the analysis of the width of the polarization deep in magnetic field we conclude that the competition between the dark exciton pseudospin relaxation and the decay of the dark exciton population into the localized states are rather different in these two materials which are representative of the two extreme cases for the ratio of relaxation rate and depolarization rate.