Abstract
Molecules constitute compact hybrid quantum optical systems that can interface photons, electronic degrees of freedom, localized mechanical vibrations and phonons. In particular, the strong vibronic interaction between electrons and nuclear motion in a molecule resembles the optomechanical radiation pressure Hamiltonian. While molecular vibrations are often in the ground state even at elevated temperatures, one still needs to get a handle on decoherence channels associated with phonons before an efficient quantum optical network based on opto-vibrational interactions in solid-state molecular systems could be realized. As a step towards a better understanding of decoherence in phononic environments, we take here an open quantum system approach to the non-equilibrium dynamics of guest molecules embedded in a crystal, identifying regimes of Markovian versus non-Markovian vibrational relaxation. A stochastic treatment based on quantum Langevin equations predicts collective vibron-vibron dynamics that resembles processes of sub- and superradiance for radiative transitions. This in turn leads to the possibility of decoupling intramolecular vibrations from the phononic bath, allowing for enhanced coherence times of collective vibrations. For molecular polaritonics in strongly confined geometries, we also show that the imprint of opto-vibrational couplings onto the emerging output field results in effective polariton cross-talk rates for finite bath occupancies.
Highlights
Molecules are natural quantum mechanical platforms where several atoms are interlinked via electronic bonds
We have provided a new approach based on quantum Langevin equations for the analysis of the fundamental quantum states of molecules and their coupling to their surroundings. These features, which lie at the heart of molecular polaritonics, go well beyond the electronic degrees of freedom and address phenomena such as electron-vibron and electronphonon couplings as well as vibron-phonon interactions resulting in the relaxation of molecular vibrations
We have presented a model of vibrational relaxation that takes into account the structure of the surrounding phonon bath and makes a distinction between Markovian and non-Markovian regimes
Summary
Molecules are natural quantum mechanical platforms where several atoms are interlinked via electronic bonds. Earlier theoretical works have either traced out the typically fast vibrational degrees of freedom [16,17], used limited numerical simulations, or focused mostly on aspects such as vibrational relaxation in solids [18,19,20,21], electron-phonon and electron-vibron couplings [22,23,24], temperature dependence of the zero-phonon linewidth [25,26] and anharmonic effects [27,28] It should be borne in mind that the relevance of our treatment is not restricted to the physical system considered here as very similar effects occur in related solid-state emitters such as quantum dots or vacancy centers in diamond.
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