We develop a quantum mechanical formalism to treat the strong coupling between an electromagnetic mode and a vibrational excitation of an ensemble of organic molecules. By employing a Bloch-Redfield-Wangsness approach, we show that the influence of dephasing-type interactions, i.e., elastic collisions with a background bath of phonons, critically depends on the nature of the bath modes. In particular, for long-range phonons corresponding to a common bath, the dynamics of the 'bright state' (the collective superposition of molecular vibrations coupling to the cavity mode) is effectively decoupled from other system eigenstates. For the case of independent baths (or shortrange phonons), incoherent energy transfer occurs between the bright state and the uncoupled dark states. However, these processes are suppressed when the Rabi splitting is larger than the frequency range of the bath modes, as achieved in a recent experiment (Shalabney et al 2015 Nat. Commun. 6 5981). In both cases, the dynamics can thus be described through a single collective oscillator coupled to a photonic mode, making this system an ideal candidate to explore cavity optomechanics at room temperature. OPEN ACCESS RECEIVED

In this Letter we analyze theoretically how the emergence of collective strong coupling between vibrational excitations and confined cavity modes affects Raman scattering processes. This work is motivated by recent experiments [Shalabney et al., Angew. Chemie 54, 7971 (2015)], which reported enhancements of up to three orders of magnitude in the Raman signal. By using different models within linear response theory, we show that the total Raman cross section is maintained constant when the system evolves from the weak-coupling limit to the strong-coupling regime. A redistribution of the Raman signal among the two polaritons is the main fingerprint of vibrational strong coupling in the Raman spectrum.Comment: 5 pages, 3 figure

Gauge fields play important roles in condensed matter, explaining for example nonreciprocal and topological transport phenomena. Establishing gauge potentials for phonon transport in nanomechanical systems would bring quantum Hall physics to a new domain, which offers broad applications in sensing and signal processing, and is naturally associated with strong nonlinearities and thermodynamics. In this work, we demonstrate a magnetic gauge field for nanomechanical vibrations in a scalable, on-chip optomechanical system. We exploit multimode optomechanical interactions, which provide a useful resource for the necessary breaking of time-reversal symmetry. In a dynamically modulated nanophotonic system, we observe how radiation pressure forces mediate phonon transport between resonators of different frequencies, with a high rate and a characteristic nonreciprocal phase mimicking the Aharonov-Bohm effect. We show that the introduced scheme does not require high-quality cavities, such that it can be straightforwardly extended to explore topological acoustic phases in many-mode systems resilient to realistic disorder.Recent years have seen the emergence of theoretical and experimental efforts exploring exotic transport phenomena in bosonic systems exploiting broken structural and temporal symmetries [1][2][3]. Magnetic gauge potentials play a particularly important role in those efforts. They can break time-reversal symmetry for transport, imparting a nonreciprocal, direction-dependent phase on a particle's wavefunction. For electrons, this leads to the celebrated Aharonov-Bohm effect [4] as well as the integer quantum Hall effect, which offers topologically protected transport in extended systems. Periodic modulation has been proposed to create synthetic gauge fields to achieve similarly rich phenomena: It allows to effectively break time-reversal symmetry and explore emergent phases for electrons [5], but importantly also for chargeless excitations of cold atoms and ions [6,7], light [8,9] and mechanics [10]. Cavity optomechanics provides a natural platform to realize time-varying potentials for either light or sound, and has been used to demonstrate nonreciprocal control of photons and phonons recently [11][12][13][14][15][16][17]. In manymode optomechanical lattices, the phase and amplitude of interactions could be controlled with optical fields to induce exotic topological phases of light and sound at the nanoscale [18][19][20]. These inspiring proposals, however, require high quality factors and put extreme demands on fabrication tolerances and control intensities to achieve sufficiently strong interactions.Here we introduce a new mechanism to establish a magnetic gauge potential for sound at the nanoscale to overcome those challenges. It relies on optically-mediated mechanical mode transfer, which arises naturally in a system that dispersively couples two mechanical modes to a single optical cavity driven with a detuned laser [21]: A displacement of one mechanical mode then shifts the cavity resonance, modifying...

Conventional approaches to probing ultrafast molecular dynamics rely on the use of synchronized laser pulses with a well-defined time delay. Typically, a pump pulse excites a wavepacket in the molecule. A subsequent probe pulse can then dissociates or ionizes the molecule, and measurement of the molecular fragments provides information about where the wavepacket was for each time delay. In this work, we propose to exploit the ultrafast nuclear-position-dependent emission obtained due to large light-matter coupling in plasmonic nanocavities to image wavepacket dynamics using only a single pump pulse. We show that the time-resolved emission from the cavity provides information about when the wavepacket passes a given region in nuclear configuration space. This approach can image both cavity-modified dynamics on polaritonic (hybrid light-matter) potentials in the strong light-matter coupling regime as well as bare-molecule dynamics in the intermediate coupling regime of large Purcell enhancements, and provides a new route towards ultrafast molecular spectroscopy with plasmonic nanocavities. :1907.12607v1 [cond-mat.mes-hall] arXiv

We calculate the exact many-body time dynamics of polaritonic states supported by an optical cavity filled with organic molecules. Optical, vibrational and radiative processes are treated on an equal footing employing the Time-Dependent Variational Matrix Product States algorithm. We demonstrate signatures of non-Markovian vibronic dynamics and its fingerprints in the far-field photon emission spectrum at arbitrary light-matter interaction scales, ranging from the weak to the strong coupling regimes. We analyze both the single and many-molecule cases, showing the crucial role played by the collective motion of molecular nuclei and dark states in determining the polariton dynamics and the subsequent photon emission.