Tatiana Ivanova | Searcharxiv

arXiv2023

Photoluminescence imaging of single photon emitters within nanoscale strain profiles in monolayer WSe$_2$

Local deformation of atomically thin van der Waals materials provides a powerful approach to create site-controlled chip-compatible single-photon emitters (SPEs). However, the microscopic mechanisms underlying the formation of such strain-induced SPEs are still not fully clear, which hinders further efforts in their deterministic integration with nanophotonic structures for developing practical on-chip sources of quantum light. Here we investigate SPEs with single-photon purity up to 98% created in monolayer WSe$_2$ via nanoindentation. Using photoluminescence imaging in combination with atomic force microscopy, we locate single-photon emitting sites on a deep sub-wavelength spatial scale and reconstruct the details of the surrounding local strain potential. The obtained results suggest that the origin of the observed single-photon emission is likely related to strain-induced spectral shift of dark excitonic states and their hybridization with localized states of individual defects.

cond-mat.mes-hall↗

arXiv2022

Dynamical Control of Interlayer Excitons and Trions in WSe$_2$/Mo$_{0.5}$W$_{0.5}$Se$_2$ Heterobilayer via Tunable Near-Field Cavity

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.

cond-mat.mtrl-sci↗