Boosting the Emission of Momentum Indirect Interlayer Excitons by an Optical Near Field in Misaligned 2D Heterostructures

The moiré superlattice potential in van der Waals heterostructures localizes the interlayer excitons and modifies the band structure so that their emission wavelength can be adjusted substantially. However, twisted structures suffer from poor emission quantum yield and long radiative lifetimes due to the angle-induced momentum mismatch. Moreover, the vertical orientation of the interlayer exciton hampers the collection efficiency. Here, we demonstrate that these unfavorable conditions can be fully overcome by embedding the heterostructure in a plasmonic circular nanocavity. By adjusting the cavity radius, the emission enhancement factor for the interlayer excitons can exceed 4 orders of magnitude due to the synergistic effect of photon momentum enlargement and promotion of the excitation rate, quantum yield, and collection efficiency by the optical near field. This strategy for engineering light-matter interactions can make these atomically thin heterostructures as alluring as their direct-band-gap opponents in the field of optoelectronics.