Model Prediction of Self-Rotating Excitons in Two-Dimensional Transition-Metal Dichalcogenides

TL;DR

This paper demonstrates that Dirac excitons in 2D transition-metal dichalcogenides inherently possess self-rotation due to Berry curvature, significantly impacting their spectral properties and resolving previous measurement discrepancies.

Contribution

It introduces a model showing intrinsic angular momentum in Dirac excitons, revealing topological self-rotation effects in 2D TMDs.

Findings

Self-rotation modifies exciton spectrum

Resolves overestimated polarizability issue

Highlights topological effects in exciton behavior

Abstract

Using the quasiclassical concept of Berry curvature we demonstrate that a Dirac exciton - a pair of Dirac quasiparticles bound by Coulomb interactions - inevitably possesses an intrinsic angular momentum making the exciton effectively self-rotating. The model is applied to excitons in two-dimensional transition metal dichalcogenides, in which the charge carriers are known to be described by a Dirac-like Hamiltonian. We show that the topological self-rotation strongly modifies the exciton spectrum and, as a consequence, resolves the puzzle of the overestimated two-dimensional polarizability employed to fit earlier spectroscopic measurements.