Strong Valley Zeeman Effect of Dark Excitons in Monolayer Transition Metal Dichalcogenides in a Tilted Magnetic Field

TL;DR

This paper develops a theoretical model to explain how dark excitons in monolayer TMDs respond to tilted magnetic fields, revealing significant splitting and brightening effects observable in photoluminescence spectra.

Contribution

The authors present a quantitative four-band Hamiltonian model that accurately reproduces experimental PL spectra and predicts dark exciton behavior under tilted magnetic fields in TMDs.

Findings

Dark exciton peaks brighten with in-plane magnetic field component.

Dark exciton peaks split more than twice as much as bright excitons.

Proposed experimental setup to observe dark exciton splitting.

Abstract

The dependence of the excitonic photoluminescence (PL) spectrum of monolayer transition metal dichalcogenides (TMDs) on the tilt angle of an applied magnetic field is studied. Starting from a four-band Hamiltonian we construct a theory which quantitatively reproduces the available experimental PL spectra for perpendicular and in-plane magnetic fields. In the presence of a tilted magnetic field, we demonstrate that the dark exciton PL peaks brighten due to the in-plane component of the magnetic field and split for light with different circular polarization as a consequence of the perpendicular component of the magnetic field. This splitting is more than twice as large as the splitting of the bright exciton peaks in tungsten-based TMDs. We propose an experimental setup that will allow to access the predicted splitting of the dark exciton peaks in the PL spectrum.