The effect of dielectric environment on the brightening of neutral and charged dark excitons in WSe$_2$ monolayer

TL;DR

This study explores how different dielectric environments influence the magnetic field-induced brightening of dark excitons in WSe$_2$ monolayers, revealing environment-dependent brightening rates and energy levels.

Contribution

It provides new insights into how dielectric surroundings affect dark exciton properties and their magnetic brightening in monolayer WSe$_2$, a topic not extensively studied before.

Findings

Brightening rates depend on dielectric environment.

Dielectric media influence energy levels of dark excitons.

Carrier concentration variation may explain brightening differences.

Abstract

The dielectric environment of atomically-thin monolayer (ML) of semiconducting transition metal dichalcogenides affects both the electronic band gap and the excitonic binding energy in the ML. We investigate the effect of the environment on the in-plane magnetic field brightening of neutral and charged dark exciton emissions in the WSe$_2$ ML. The monolayers placed in three dielectric environments are studied, in particular, the ML encapsulated in hexagonal BN (hBN) flakes, the ML deposited on a hBN layer, and the ML embedded between the hBN flake and SiO$_2$/Si substrate. We observe that the brightening rates of the neutral and charged dark excitons depend on the dielectric environment, which may be related to the variation of the level of carrier concentration in the ML. Moreover, the surrounding media, characterized by different dielectric constants, influences weakly the relative energies of the neutral and charged dark excitons in reference to the bright ones.