Optically active neutral and charged single photon emitters in atomically thin materials

Atomically thin materials with honeycomb lattice have intriguing opto-electronic properties due to strong carrier interactions and the presence of additional electronic degree of freedoms such as the valley pseudospin. Recently, single photon emitters (SPE) in atomically thin transition metal dichalcogenides such as WSe2 have been reported which, possibly arise from excitons trapped in shallow potentials. We perform low-temperature magneto-optical spectroscopy on WSe2 quantum dots (QD) in field effect transistor geometry. Correlations of spectral wandering allows us to assign multiple peaks arising from the same QD. We observe entanglement of neutral SPE with in-plane chiral phonon modes of WSe2 (Fig. (a)). This results in unpolarized single photon emission, with the polarization recovered in an out-of-plane magnetic field. In addition, we find evidence for singly charged quantum dots with an excess spin. We demonstrate optical initialization of single spin with the helicity of incident light (Fig. (b)). Our findings open up ways for valleytronic based quantum optics in 2D materials.

Fig. (a) Schematic depicting entanglement of neutral SPE with chiral phonons (b) Photoluminescence measurements demonstrating initialization of single spin with helicity of incident light