Philip Kim1
Harvard University1
Atomically thin semiconductor heterostructures based on transition metal dichalcogenides (TMDs) offer an electrically tunable platform for developing coherent on-chip optoelectronic devices. Interlayer excitons (IEs) in these systems form out-of-plane dipoles and exhibit long lifetimes owing to the spatial separation of electrons and holes. The bosonic nature of excitons and strong dipolar interactions make them ideal candidates for searching for Bose-Einstein condensation in 2D materials. In this presentation, I will discuss creating high densities of cold, controllable excitons as an essential step toward studying the phase diagram of dipolar exciton gases in MoSe2/WSe2 atomically thin heterostructures. Via electrostatic gating, we spatially modulate the vertical electric fields to create a quasi-1D trap for the diffusive IEs, enabling control over the spatial diffusion profile and local IE densities. By electrically modulating density, we reveal a universal linewidth broadening at a critical density in good agreement with the Mott density, independent of the local electrostatic profile. In the second part of the talk, I will demonstrate coherent light emission from the IEs formed by electrically driven carrier injection. We observe a threshold in the electroluminescence of interlayer excitons as we increase the applied forward bias with a balanced injection of electrons and holes. We further characterize the nature of this transition by performing measurements of the second-order correlation function. Strong photon number correlation has been characterized near the threshold IE emission, signaling the quantum correlation of IEs in this regime.