Anomalous energy shift of laterally confined two-dimensional excitons

TL;DR

This paper presents a theoretical study of how the energy of confined 2D excitons in monolayer quantum dots depends on size, material properties, and edge effects, explaining recent experimental observations.

Contribution

It introduces a nonlocal screening model for exciton energy in circular 2D monolayers, including the impact of a dead layer at the edge, which is a novel aspect.

Findings

Exciton energy depends on circle radius, reduced mass, and susceptibility.

A dead layer at the edge is essential to explain observed energy shifts.

The model aligns with recent experimental data on monolayer WSe2 quantum dots.

Abstract

We theoretically investigate the energy of the ground state exciton confined to two-dimensional (2D) monolayers with circular shape. Within an effective mass approach employing a nonlocal screening effect on the Coulomb potential energy, we demonstrate how the exciton energy is correlated with the radius of the circle, electron-hole reduced mass, and 2D susceptibility. In addition, we show that a dead layer around the circle edge, into which the electron-hole pair cannot penetrate, is necessary for understanding the energy shift recently observed in monolayer WSe2 quantum dots.