Non-Markovian polariton dynamics in organic strong coupling

Abstract

Strongly coupled organic systems are characterized by unusually large Rabi splittings, even in the vacuum state. They show the counter-intuitive feature of a lifetime of the lower polariton state longer than for all other excited states. Here we build up a new theoretical framework to understand the dynamics of such coupled system. In particular, we show that the non-Markovian character of the relaxation of the dressed organic system explains the long lifetime of the lower polariton state.

Modified relaxation dynamics and coherent energy exchange in coupled vibration-cavity polaritons

“…The excitation pulse promotes ground-state W(CO) 6 to the LP and UP. This reduction in ground-state population leads to reduced absorption and, therefore, reduced splitting, similar to phenomena observed in exciton polaritons37384445. The probe pulse measures the excited-state spectrum of the non-equilibrium distribution of ground state, LP-, UP- and reservoir - excited W(CO) 6 .…”

“…Transient spectroscopic techniques have revealed significantly modified dynamics in cavity-coupled electronic states36 and direct energy transfer between the two cavity-coupled polariton states243738. In the present communication, we report the transient pump–probe spectroscopy of a cavity-coupled vibrational mode.…”

Ultra-strong coupling of molecular materials: spectroscopy and dynamics

“…As a consequence, the energy level of the lower polariton branch lies amongst the higher vibrational states of the ground state manifold. 47 Thus, even if the polariton state is formed efficiently, it will relax very efficiently by dissipating energy into this bath of non-radiative states. This is despite the fact that polaritons, generated by excitation to PÀ or P+, are expected to interact (scatter) very weakly with phonons due to their low effective mass (being quasi-bosons).…”

“…In addition, organic molecules used in strong coupling have typically 100 to 200 normal vibrational modes that also have strong consequences on their properties. 32,46,47 With vacuum Rabi splittings (ħU RV ) in the order of 1 eV, importantly, the coupled system is no longer in the Markovian regime since ħU RV [ k B T. 47 As a consequence, the lifetimes of the polaritonic states P+ and PÀ cannot be predicted from the lifetimes of the constituents of the system, namely the lifetime of the photon in the cavity and lifetime of the excited state. As we have pointed out elsewhere, 32 there are numerous examples of coupled systems that are longer lived than their constituents, for instance in the case of molecular excimers and exciplexes.…”

Quantum theory of collective strong coupling of molecular vibrations with a microcavity mode

“…When the molecule-cavity coupling is comparable to or faster than the decay of bath correlations Ω ω ≳ ( ) R cut , this is an invalid approximation, and it is crucial to include the full system Hamiltonian when deriving the master equation to satisfy detailed balance [23]. This point was also stressed in a recent paper in the context of electronic strong coupling [24], based on a phenomenological model of the system.…”