Tip-enhanced nano-optical trapping spectroscopy for self-induced strong coupling of a single quantum emitter

Plasmonic nano-optical tweezers provide precise trapping of nanoscale objects, such as nanoparticles and molecules, even at the single-particle level. However, static plasmonic tweezers face limitations in active control, including deterministic positioning, force magnitude, and the ability to capture and release objects on demand. Combining them with atomic force microscopy (AFM) presents a promising avenue for advanced study of nano-optical trapping, yet the simultaneous operation of AFM and optical spectroscopy in liquid environments remains a challenge. Here, we present tip-enhanced nano-optical trapping (TENT) spectroscopy, enabling robust strong coupling of single quantum dots (QDs) in liquid. By utilizing tip-enhanced gradient forces and torque, we achieve highly reproducible nano-optical trapping and self-alignment of individual QDs. The trapped and aligned QD within the tip-cavity forms hybrid quantum states of plexcitons in the strong coupling regime and shows the self-induced back action (SIBA) effect, as revealed by real-time spectroscopic measurements of near-field photoluminescence. This work provides a new strategy for studying light-matter interactions in liquid environments at an unprecedented level, using an advanced nano-optical trapping approach.