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arXiv · 2112.04781

Chirality of Valley Excitons in Monolayer Transition-Metal Dichalcogenides

Fabio Caruso·Maximilian Schebek·Yiming Pan·Cecilia Vona·Claudia Draxl
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Abstract

By enabling control of valley degrees of freedom in transition-metal dichalcogenides, valley-selective circular dichroism has become a key concept in valleytronics. In this manuscript, we show that valley excitons -- bound electron-hole pairs formed at either the K or K' valleys upon absorption of circularly-polarized light -- are chiral quasiparticles characterized by a finite orbital angular momentum (OAM). We further formulate an ab-initio many-body theory of valley-selective circular dichroism and valley excitons based on the Bethe-Salpeter equation. Beside governing the interaction with circularly polarized light, the OAM confers excitons a finite magnetization which manifests itself through an excitonic Zeeman splitting upon interaction with external magnetic fields. The good agreement between our ab-initio calculations and recent experimental measurements of the exciton Zeeman shifts corroborate this picture.

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Fabio Caruso, Maximilian Schebek, Yiming Pan, Cecilia Vona, Claudia Draxl. 2021-12-09. Chirality of Valley Excitons in Monolayer Transition-Metal Dichalcogenides. https://doi.org/10.1021/acs.jpclett.2c01034

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