Room-Temperature, Strong Emission of Momentum-Forbidden Interlayer Excitons in Nanocavity-Coupled Twisted van der Waals Heterostructures

The emission efficiency of interlayer excitons (IEs) in twisted 2D heterostructures has long suffered from momentum mismatch, limiting their applications in ultracompact excitonic devices. Here, we report strong room-temperature emission of momentum-forbidden IE in 30°-twisted MoS2/WS2 heterobilayers. Utilizing a plasmonic nanocavity, the Purcell effect boosts the IE emission intensity in the cavity by over 2 orders of magnitude. We further study the interplay of this Purcell enhancement and phonon assistance in 30°- and 0°-twisted heterostructures. Temperature-dependent and time-resolved spectroscopy reveal that the IE enhancement in 30°-twisted cases involves competition between IEs and intralayer excitonic emission, which is remarkably distinct from the 0°-twisted cases. We propose a comprehensive exciton decay model capturing the features of the phonon-assisted momentum compensation and the Purcell enhancement of the IE emission, showing consistency with the experimental measurements. Our results enrich the understanding of the nanocavity-assisted light–matter interaction for momentum-indirect excitonic transitions.