# Magnetically-Sensitive Valley Polarization Reversal and Revival of Defect-Localized Excitons in WSe2-WS2

## TL;DR

This study demonstrates magnetic field control over valley polarization in defect-localized excitons within WSe2-WS2 heterobilayers, revealing reversal and revival phenomena that enhance understanding of valley dynamics in TMDs.

## Contribution

It uncovers magnetic field-induced reversal and revival of valley polarization in defect-localized excitons, a novel control mechanism in TMD heterostructures.

## Key findings

- Valley polarization can be reversed by weak magnetic fields in interlayer defect excitons.
- Valley polarization can be revived after decay in intralayer defect excitons under moderate magnetic fields.
- Defect-localized excitons exhibit microsecond lifetimes, enabling magnetic manipulation.

## Abstract

Manipulating and reserving the valley pseudospin of excitons is one core aim in the two-dimensional transition metal dichalcogenides (TMDs). However, due to the strong electron-hole exchange and spin-orbit coupling interactions, the exciton recombination lifetime is subject to picosecond timescale intrinsically, and the valley polarization is hardly modulated by a moderate magnetic field. It is fortunate that interlayer and defect-localized excitons promise to overcome these difficulties by suppressing the above interactions. Here we clearly reveal that the valley polarization can be reversed and revived in the defect-localized excitons with a microsecond lifetime in AB-stacked WSe2-WS2 heterobilayer. Specifically, for the interlayer defect-localized exciton, the valley polarization is reversed and can be efficiently enhanced by a weak out-of-plane magnetic field (<0.4 T). In sharp contrast, the valley polarization of the intralayer defect-localized exciton can revive after a fast decay process and follows the direction of the moderate out-of-plane magnetic field (<3 T). We explain the reversed valley polarization with highly magnetic sensitivity by the delocalization of defect-localized holes under a weak magnetic field and the revival of valley polarization by the valley Zeeman effect under a moderate magnetic field. Our results demonstrate that the valley pseudospin of defect-localized excitons can be efficiently modulated by the external magnetic field and enrich both the understanding and the technical approaches on manipulating the valley dynamics in TMDs and their heterostructure.

---
Source: https://tomesphere.com/paper/1903.06899