Tip-enhanced photoluminescence and control of interlayer excitons in van der Waals heterostructures

Two-dimensional (2D) van der Waals heterostructures have emerged as attractive candidates for applications in novel electro-optical devices due to their rich excitonic properties. Transition metal dichalcogenide (TMD) heterostructures are particularly promising candidates in which interlayer excitons were recently observed in the far field. However, the details of interlayer exciton behavior at variable interlayer distances and the mechanisms underlying the interlayer coupling have yet to be understood. We show that optical-antenna tip coupling in tip-enhanced photoluminescence (TEPL) imaging induces radiative pathways with highly enhanced PL emission through both the Purcell effect and the ability of the antenna-tip to couple to out-of-plane exciton dipole moments. Furthermore, we show precise nano-resonator gap engineering of the van der Walls heterostructure by nano-mechanical tip force control. Using this approach, we measure and control the interlayer exciton properties of a MoSe₂-WSe₂ heterostructure providing insight into the interlayer coupling mechanism, and paving the way for novel nano-photonic devices.