Photoexcitation of moir\'e-trapped interlayer excitons via chiral phonons

TL;DR

This paper demonstrates a novel phonon-assisted method to excite moiré-trapped interlayer excitons in TMD heterobilayers, enabling valley-selective and helicity-controlled quantum emitter generation with potential applications in valleytronics and quantum photonics.

Contribution

It introduces a new phonon-assisted excitation mechanism involving chiral in-plane optical phonons, supported by experimental and first-principles calculations, for controlled quantum emitter generation in TMD moiré systems.

Findings

Identified a fixed phonon energy of ~23 meV mediating excitation.

Demonstrated valley-selective optical excitation of interlayer excitons.

Supported by first-principles calculations confirming phonon mode symmetry and energy.

Abstract

Moir\'e superlattices in transition-metal dichalcogenide semiconductor heterobilayers enable the quantum confinement of interlayer excitons with large out-of-plane permanent electric dipoles and spin-valley control. Here, we report a novel phonon-assisted excitation mechanism of individual moir\'e-trapped interlayer excitons in 2H-stacked MoSe$_2$/WSe$_2$ heterobilayers via chiral $E^{\prime\prime}$ in-plane optical phonons at the {\Gamma}-point. This excitation pathway preserves valley-selective optical selection rules and enables deterministic generation of individual interlayer excitons with defined helicity, emitting within a spectrally narrow energy spread. Through photoluminescence excitation spectroscopy in both the ensemble and quantum emitter regimes, we identify a fixed phonon energy of $\sim$23 meV mediating the process. First-principles calculations corroborate the symmetry and energy of the relevant phonon mode and its coupling to interlayer excitons, providing microscopic support for the observed valley-selective phonon-assisted excitation mechanism. Our results highlight the utility of chiral phonons as a tool for controlled excitation of quantum emitters in TMD moir\'e systems, opening new opportunities for valleytronic and quantum photonic applications.