Rabi-vibronic resonance with large number of vibrational quanta

Abstract

We study theoretically the Rabi oscillations of a resonantly driven two-level system linearly coupled to a harmonic oscillator (vibrational mode) with frequency ${\ensuremath{\omega}}_{0}$. We show that for weak coupling, ${\ensuremath{\omega}}_{p}\ensuremath{\ll}{\ensuremath{\omega}}_{0}$, where ${\ensuremath{\omega}}_{p}$ is the polaronic shift, Rabi oscillations are strongly modified in the vicinity of the Rabi-vibronic resonance ${\ensuremath{\Omega}}_{R}={\ensuremath{\omega}}_{0}$, where ${\ensuremath{\Omega}}_{R}$ is the Rabi frequency. The width of the resonance is $({\ensuremath{\Omega}}_{R}\ensuremath{-}{\ensuremath{\omega}}_{0})\ensuremath{\sim}{\ensuremath{\omega}}_{p}^{2/3}{\ensuremath{\omega}}_{0}^{1/3}\ensuremath{\gg}{\ensuremath{\omega}}_{p}$. Within this domain of ${\ensuremath{\Omega}}_{R}$ the actual frequency of the Rabi oscillations exhibits a bistable behavior as a function of ${\ensuremath{\Omega}}_{R}$. Importantly, within the resonant domain, the oscillator is highly excited, which allows us to treat it classically.