Fine-tuning biexcitons-plasmon coherent states in a single nanocavity

Abstract

A tunable plexcitonic material that sustains multimode hybridization is highly desirable, which is vital for advanced quantum devices. However, the research about regulations of biexcitons-plasmon coherent states has rarely been reported. Here we apply single-nanoparticle scattering spectroscopy correlative with SEM imaging to identify biexcitons-plasmon interaction in a metal-semiconductor hybrid structure composed of a single Au@Ag nanoparticle, J-aggregates molecules and tungsten disulfide (WS2) monolayer. The mode competition within the localized plasmonic hotspots (∼240 nm3) is revealed by continuously regulating the J-aggregates spacer. Two distinct anticrossings are observed at both excitons resonances, and large double Rabi splittings (137 meV and 124 meV) are obtained successfully. We establish experimentally that J-aggregates and WS2 monolayer are responsible for the middle polariton states, while plasmon rarely contributes. Further calculations show that plasmonic nanocavity enables coherent energy exchange with different excitons by providing a highly enhanced localized E-field. In addition, we find that the multimode coupling strengths can be efficiently tuned by changing the cavity morphology and environment temperature, where the tuning spectral accuracy can reach up to 1 nm. Our findings uncover the distinctive properties of biexcitons-plasmon polaritons, suggest an easily obtainable multiqubit states platform, and open up a new way to construct nanoscale photonic devices.

The Mechanism of Manipulating Chirality and Chiral Sensing Based on Chiral Plexcitons in a Strong-Coupling Regime

“…The CD spectra do not show intermediate states due to the uncoupling between the bonding and antibonding modes. The CD spectra behave more as a combination of two strong coupled systems, unlike the common three-mode polariton coupling, where intermediate coupling states occur [ 40 ].…”

“…The CD spectra do not show intermediate states due to the uncoupling between the bonding and antibonding modes. The CD spectra behave more as a combination of two strong coupled systems, unlike the common three-mode polariton coupling, where intermediate coupling states occur [40]. As shown in Figure 3d, we calculated the energy distribution of the plexcitonic system according to Equation (2), and it can be observed that the bonding mode and the antibonding mode are strongly coupled with the excitons.…”

Strong Plasmon-Exciton Coupling in Colloidal Cubic Nanoparticles and Layered Molecular J-aggregates

“…These values align with previously reported results for strong coupling between J-aggregates and Au nanoparticles. 26,28,30,40,50,52,53 For the TDBC J-aggregates, a higher g-value was obtained for the AuNSs compared to the AuNCs, attributable to the increased number of molecules involved in the coupling process. For nanoparticles of the same type, specifically AuNC(66)-PIC, their coupling strength was found to be lower than that of AuNC(74)-TDBC, primarily due to the weaker interaction between the J-aggregates and nanoparticle surfaces, a consequence of their same charge signs.…”

Triple Plexcitonic Nonreciprocity of Magnetochiral Plexcitons

“…44 Due to the great advantages in miniaturization, stability, and finecontrollability, strongly coupled systems of metal plasmonic nanocavities−emitters have become a significant research direction in room-temperature strong coupling. 45,46 More noteworthy, recent advances have combined plexcitons with a single broken symmetry to unlock their rich many-body nature, greatly promoting the fields of chiroptics, magneto-optics, and polariton physics. 47−54 However, in conventional plasmonic hybrid nanocavities governed by single asymmetrical plexcitons, such as chiral plexcitons 47−49 and magnetically dressed plexcitons, 50−52 transition metal dihalides (TMDs)−magnetic medium, we demonstrate the triple plexcitonic nonreciprocity of magnetochiral plexcitons with flexible controllability.…”

“…Recently, room-temperature strong coupling between quantum emitters and plasmons has attracted a lot of attention in optical and quantum physics. − In the strong light–matter coupling regime, the energy exchange between plasmons and matter excitations becomes faster than the dissipation and decoherence, producing new optical hybrid states called plexcitons. − Plexcitons can facilitate studies of coherent energy transfer, quantum entanglement, Bose–Einstein condensation, and other quantum phenomena, − exhibiting great potential in quantum light sources, , single-molecule sensing, and quantum computing . Due to the great advantages in miniaturization, stability, and fine-controllability, strongly coupled systems of metal plasmonic nanocavities–emitters have become a significant research direction in room-temperature strong coupling. , More noteworthy, recent advances have combined plexcitons with a single broken symmetry to unlock their rich many-body nature, greatly promoting the fields of chiroptics, magneto-optics, and polariton physics. − However, in conventional plasmonic hybrid nanocavities governed by single asymmetrical plexcitons, such as chiral plexcitons − and magnetically dressed plexcitons, − nonreciprocity is missing. The absence of a plexcitonic nonreciprocal mechanism limits the development of optical technologies dominated by light–matter polaritons.…”