Single-exciton trapping in an electrostatically defined two-dimensional semiconductor quantum dot

Interlayer excitons (IXs) in two-dimensional semiconductors have long lifetimes and spin-valley coupled physics, with a long-standing goal of single-exciton trapping for valleytronic applications. In this work, we use a nanopatterned graphene gate to create an electrostatic IX trap. We measure a unique power-dependent blueshift of IX energy, where narrow linewidth emission exhibits discrete energy jumps. We attribute these jumps to quantized increases of the number occupancy of IXs within the trap and compare to a theoretical model to assign the lowest energy emission line to single-IX recombination.