Steering valley-polarized emission of monolayer MoS₂ sandwiched in plasmonic antennas

Monolayer transition metal dichalcogenides (TMDCs) have intrinsic spin-valley degrees of freedom, making it appealing to exploit valleytronic and optoelectronic applications at the nanoscale. Here, we demonstrate that a chiral plasmonic antenna consisting of two stacked gold nanorods (GNRs) can modulate strongly valley-polarized photoluminescence (PL) of monolayer MoS₂ in a broad spectral range at room temperature. The valley-polarized PL of the MoS₂ with the antenna can reach up to ~48% accompanied with more than three orders of magnitude enhancement of PL intensity. Also, the K and K’ valleys under opposite circularly polarized light excitation exhibit different emission intensities and directivities in the far-field, which can be attributed to the valley-dependent exciton modulation by the chiral antenna in both excitation and emission processes. The distinct features of the ultra-compact hybrid suggest potential applications for valleytronic and photonic devices, chiral quantum optics, and high-sensitive detection.