Interlayer exciton flux amplification driven by strong exciton confinement.

The complex but extraordinary transport properties of interlayer excitons (IXs) in van der Waals heterostructures drive the development of advanced excitonic circuits, yet their transport mechanisms at the nanoscale remain largely unknown. Here we demonstrate an anomalous IX transport regime arising from nanoscale bandgap modifications in van der Waals heterostructures. To manipulate and simultaneously probe such IX behaviour, we use a controllable electro-plasmonic nanocavity with subnanometre positional precision. The nanoscale bandgap gradient confines IXs to a narrow potential well, creating a highly localized density profile whose outward diffusion current exceeds the electric-field-induced drift. We quantify an ~8,300% amplification of the diffusion current compared with that achieved using conventional microscale gating. Moreover, this anomalous regime is not governed by the total IX population, but by the nanoscale IX density gradient. Our work reveals a decoupling of IX transport efficiency from density constraints, establishing nanocavity confinement for reconfigurable exciton flux in van der Waals devices.