Electrostatic single exciton trapping in a 2D semiconductor heterostructure using nanopatterned graphene

Interlayer excitons (IXs) in 2D semiconductors have long lifetimes and spin-valley coupled physics, with a long-standing goal of single exciton trapping for quantum applications. In this work, we use a nano-patterned graphene gate to create an electrostatic IX trap. In photoluminescence measurements, we observe narrow linewidth emission, which is a signature of strong spatial confinement, and a unique power-dependent blue-shift of IX energy, with jumps between discrete emission energies. We attribute these jumps to quantized increases of the number occupancy of IXs within the trap. We compare these results to a theoretical model to assign the lowest energy emission line to single IX recombination, indicating that we can create a population of a single exciton within our trap using low laser excitation power. These traps are advantageous over other trapping methods involving strain or moiré potentials due to their deterministic lithographically defined process, 100 meV energy tunability by applied gate voltage, and scalability to create large arrays of single quantum emitters with controllable placement.