Single-molecule strong coupling at room temperature in plasmonic nanocavities

Abstract

Emitters placed in an optical cavity experience an environment that changes their coupling to light. In the weak-coupling regime light extraction is enhanced, but more profound effects emerge in the single-molecule strong-coupling regime where mixed light-matter states form1,2. Individual two-level emitters in such cavities become non-linear for single photons, forming key building blocks for quantum information systems as well as ultra-low power switches and lasers3–6. Such cavity quantum electrodynamics has until now been the preserve of low temperatures and complex fabrication, severely compromising their use5,7,8. Here, by scaling the cavity volume below 40 nm3 and using host-guest chemistry to align 1-10 protectively-isolated methylene-blue molecules, we reach the strong-coupling regime at room temperature and in ambient conditions. Dispersion curves from >50 plasmonic nanocavities display characteristic anticrossings, with Rabi frequencies of 300 meV for 10 molecules decreasing to 90 meV for single molecules, matching quantitative models. Statistical analysis of vibrational spectroscopy time-series and dark-field scattering spectra provide evidence of single-molecule strong coupling. This dressing of molecules with light can modify photochemistry, opening up the exploration of complex natural processes such as photosynthesis9 and pathways towards manipulation of chemical bonds10.

Cavity-Enhanced Transport of Charge

“…PACS numbers: 05.60. Gg, 42.50.Pq, 74.40.Gh, The study of strong light-matter interactions [1][2][3][4] is playing an increasingly crucial role in understanding as well as engineering new states of matter with relevance to the fields of quantum optics [5][6][7][8][9][10][11][12][13][14][15][16][17][18], solid state physics [19][20][21][22][23][24][25][26][27][28][29][30][31], as well as quantum chemistry [32][33][34][35][36] and material science [37][38][39][40][41][42][43][44][45][46][47][48][49][...…”

Transformation Optics Approach to Plasmon-Exciton Strong Coupling in Nanocavities

“…From the experimental side, in recent years, PEPs have been reported in emitter ensembles [10][11][12][13], in which excitonic nonlinearities are negligible [14][15][16]. Only very recently, thanks to advances in the fabrication and characterization of large Purcell enhancement nanocavities [17][18][19], far-field signatures of plasmonexciton strong coupling for single molecules have been reported experimentally [20].In this Letter, we theoretically investigate the plasmonic coupling of a single emitter in a paradigmatic cavity: the nanometric gap between two metallic particles [13,19,20]. We consider spherical-shaped nanoparticles, and develop a transformation optics (TO) [21,22] approach that fully accounts for the rich EM spectrum that originates from SP hybridization across the gap.…”

“…From the experimental side, in recent years, PEPs have been reported in emitter ensembles [10][11][12][13], in which excitonic nonlinearities are negligible [14][15][16]. Only very recently, thanks to advances in the fabrication and characterization of large Purcell enhancement nanocavities [17][18][19], far-field signatures of plasmonexciton strong coupling for single molecules have been reported experimentally [20].…”

Mode Modification of Plasmonic Gap Resonances Induced by Strong Coupling with Molecular Excitons

“…single Au nanocube-film (NC-film) resonators ( Figure 1a) that can squeeze EM fields into an extremely narrow gap (a few nanometers wide, typically less than 100 / λ ) between nanoparticles and a metallic substrate [33][34][35][36][37]. The exceptionally small V significantly enhances the density of optical states, even enabling single molecules strong coupling in the cavity [38]. Here using the NC-film resonators, we for the first time experimentally demonstrate that by doping the nano-gap with J-aggregate dye molecules, the greatly enhanced strong coupling between molecular excitons and gap plasmons not only enables the spectral Rabi splitting, but also, more importantly, shows significant modifications of far-field scattering patterns from the NC-film cavity.…”