  Emerging photo-induced excitonic processes in transition metal dichalcogenide
(TMD) heterobilayers, e.g., coupling, dephasing, and energy transfer of intra-
and inter-layer excitons, allow new opportunities for ultrathin photonic
devices. Yet, with the associated large degree of spatial heterogeneity,
understanding and controlling their complex competing interactions at the
nanoscale remains a challenge. Here, we present an all-round dynamic control of
intra- and inter-layer excitonic processes in a
WSe$_2$/Mo$_{0.5}$W$_{0.5}$Se$_2$ heterobilayer using multifunctional
tip-enhanced photoluminescence (TEPL) spectroscopy. Specifically, we control
the radiative recombination path and emission rate, electronic bandgap energy,
and neutral to charged exciton conversion with <20 nm spatial resolution in a
reversible manner. It is achieved through the tip-induced engineering of Au
tip-heterobilayer distance and interlayer distance, GPa scale local pressure,
and plasmonic hot-electron injection respectively, with simultaneous
spectroscopic TEPL measurements. This unique nano-opto-electro-mechanical
control approach provides new strategies for developing versatile
nano-excitonic devices based on TMD heterobilayers.
