Quantum confined Stark effect in a MoS$_2$ monolayer van der Waals heterostructure

TL;DR

This study investigates the quantum confined Stark effect in a MoS₂ monolayer heterostructure, demonstrating exciton polarization under an electric field and providing new polarizability measurements consistent with theory.

Contribution

It introduces a method to measure exciton Stark shifts in MoS₂ monolayers and reports polarizability values that align with theoretical predictions, advancing understanding of excitonic properties in 2D materials.

Findings

Quadratic shift of exciton emission energies with electric field.

Extracted exciton polarizabilities are consistent with theoretical models.

Methodology applicable to other layered semiconductors.

Abstract

The optics of dangling-bond-free van der Waals heterostructures containing transition metal dichalcogenides are dominated by excitons. A crucial property of a confined exciton is the quantum confined Stark effect (QCSE). Here, such a heterostructure is used to probe the QCSE by applying a uniform vertical electric field across a molybdenum disulfide (MoS$_2$) monolayer. The photoluminescence emission energies of the neutral and charged excitons shift quadratically with the applied electric field provided the electron density remains constant, demonstrating that the exciton can be polarized. Stark shifts corresponding to about half the homogeneous linewidth were achieved. Neutral and charged exciton polarizabilities of $(7.8~\pm~1.0)\times 10^{-10}~\tr{D~m~V}^{-1}$ and $(6.4~\pm~0.9)\times 10^{-10}~\tr{D~m~V}^{-1}$ at relatively low electron density ($8 \times 10^{11}~\tr{cm}^{-2}$) have been extracted, respectively. These values are one order of magnitude lower than the previously reported values, but in line with theoretical calculations. The methodology presented here is versatile and can be applied to other semiconducting layered materials as well.