The rotating excitons in two-dimensional materials: Valley Zeeman effect and chirality

TL;DR

This paper introduces a model of rotating excitons in 2D materials, revealing how their angular momentum exchange with phonons affects valley Zeeman effects and enabling new control in valleytronics.

Contribution

It proposes a novel rotational exciton model that explains valley Zeeman asymmetry and fluctuations, highlighting the role of angular momentum exchange with phonons.

Findings

Angular momentum exchange causes large g-factor fluctuations.

Asymmetry in valley Zeeman splitting depends on phononic magnetic moments.

Rotating exciton model offers new control mechanisms in valleytronics.

Abstract

We propose the rotational dynamics of the intralayer and interlayer excitons with their inherent momenta of inertia in the monolayer and bilayer transition metal dichalcogenides, respectively, where the new chirality of exciton is endowed by the rotational angular momentum, namely, the formations of left- and right-handed excitons at the +K and -K valleys, respectively. We find that angular momenta exchange between excitons and its surrounding phononic bath result in the large fluctuation of the effective g-factor and the asymmetry of valley Zeeman splitting observed in most recently experiments, both of which sensitively depend on the magnetic moments provided by the phononic environment. This rotating exciton model not only proposes a new controllable knob in valleytronics, but opens the door to explore the angular momentum exchange of the chiral quasiparticles with the many-body environment.