Quantum confined trions in a van der Waals heterostructure

Inspired by the discovery of graphene, an array of 2D materials have been isolated that exhibit a variety of interesting electronic properties. One such class being the semiconducting transition-metal dichalcogenides (TMDCs) that support optical transitions ranging from visible to NIR. Quantum confinement in these monolayers leads to strong exciton and trion resonances even at room temperature. Furthermore, the TMDCs exhibits symmetry mediated optical selection rules that couples the two inequivalent Brillouin zone K points with distinct circular polarization states. This property offers the realization of valleytronic devices. Availing the recently discovered localized quantum dot-like emissions in TMDCs, we have demonstrated controlled charging in these individual confined excitons in monolayer WSe₂ in a charge tunable van der Waals heterostructure. We show that these quantum dot trions can also inherit the polarization selection rules of the host material under certain conditions. The trion ground state is important for localized single spin studies in TMDCs. This shows potential for using TMDCs as building blocks for quantum photonic circuits that possess optically accessible ground-state spins.