Tailoring exciton dynamics in TMDC heterobilayers in the ultranarrow gap-plasmon regime

Control of excitons in transition metal dichalcogenides (TMDCs) and their heterostructures is fundamentally interesting for tailoring light-matter interactions and exploring their potential applications in high-efficiency optoelectronic and nonlinear photonic devices. While both intra- and interlayer excitons in TMDCs have been heavily studied, their behavior in the quantum tunneling regime, in which the TMDC or its heterostructure is optically excited and concurrently serves as a tunnel junction barrier, remains unexplored. Here, using the degree of freedom of a metallic probe in an atomic force microscope, we investigated both intralayer and interlayer excitons dynamics in TMDC heterobilayers via locally controlled junction current in a finely tuned sub-nanometer tip-sample cavity. Our tip-enhanced photoluminescence measurements reveal a significantly different exciton-quantum plasmon coupling for intralayer and interlayer excitons due to different orientation of the dipoles of the respective e-h pairs. Using a steady-state rate equation fit, we extracted field gradients, radiative and nonradiative relaxation rates for excitons in the quantum tunneling regime with and without junction current. Our results show that tip-induced radiative (nonradiative) relaxation of intralayer (interlayer) excitons becomes dominant in the quantum tunneling regime due to the Purcell effect. These findings have important implications for near-field probing of excitonic materials in the strong-coupling regime.

Automated summary

The exciton control in transition metal dichalcogenides (TMDCs) and their heterostructures has fundamental importance for applications in optoelectronic and photonic devices. In this study, the behavior of intra- and interlayer excitons in TMDC heterobilayers under the quantum tunneling regime was explored using a metallic probe in an atomic force microscope. The results revealed significantly different exciton-plasmon coupling for intra- and interlayer excitons due to the orientation of the dipoles of the electron-hole pairs. The findings have important implications for near-field probing of excitonic materials in the strong-coupling regime.