Tunable interlayer excitons and switchable interlayer trions via dynamic near-field cavity

Emerging photo-induced excitonic processes in transition metal dichalcogenide(TMD)heterobilayers,e.g.,interplay of intra-and inter-layer excitons and conversion of excitons to trions,allow new opportunities for ultrathin hybrid photonic devices.However,with the associated large degree of spatial heterogeneity,understanding and controlling their complex competing interactions in TMD heterobilayers at the nanoscale remains a challenge.Here,we present an all-round dynamic control of interlayer-excitons and-trions in a WSe_(2)/Mo_(0.5 )W_(0.5) Se_(2) heterobilayer using multifunctional tip-enhanced photoluminescence(TEPL)spectroscopy with<20 nm spatial resolution.Specifically,we demonstrate the bandgap tunable interlayer excitons and the dynamic interconversion between interlayer-trions and-excitons,through the combinational tip-induced engineering of GPa-scale pressure and plasmonic hot electron injection,with simultaneous spectroscopic TEPL measurements.This unique nano-opto-electro-mechanical control approach provides new strategies for developing versatile nano-excitonic/trionic devices using TMD heterobilayers.

Nonlinear polaritons in a monolayer semiconductor coupled to optical bound states in the continuum

Optical bound states in the continuum(BICs)provide a way to engineer very narrow resonances in photonic crystals.The extended interaction time in these systems is particularly promising for the enhancement of nonlinear optical processes and the development of the next generation of active optical devices.However,the achievable interaction strength is limited by the purely photonic character of optical BICs.Here,we mix the optical BIC in a photonic crystal slab with excitons in the atomically thin semiconductor MoSe_(2) to form nonlinear exciton-polaritons with a Rabi splitting of 27 meV,exhibiting large interaction-induced spectral blueshifts.The asymptotic BIC-like suppression of polariton radiation into the far field toward the BIC wavevector,in combination with effective reduction of the excitonic disorder through motional narrowing,results in small polariton linewidths below 3 meV.Together with a strongly wavevector-dependent Q-factor,this provides for the enhancement and control of polariton–polariton interactions and the resulting nonlinear optical effects,paving the way toward tuneable BIC-based polaritonic devices for sensing,lasing,and nonlinear optics.