Polariton Induced Conical Intersection and Berry Phase

We investigate the Polariton induced conical intersection (PICI) created from coupling a diatomicmolecule with the quantized photon mode inside an optical cavity, and the corresponding BerryPhase effects. We use the rigorous Pauli-Fierz Hamiltonian to describe the quantum light-matterinteractions between a LiF molecule and the cavity, and exact quantum propagation to investigatethe polariton quantum dynamics. The molecular rotations relative to the cavity polarization directionplay a role as the tuning mode of the PICI, resulting in an effective CI even within a diatomic molecule.To clearly demonstrate the dynamical effects of the Berry phase, we construct two additional modelsthat have the same Born-Oppenheimer surface, but the effects of the geometric phase are removed.We find that when the initial wavefunction is placed in the lower polaritonic surface, the Berryphase causes aπphase-shift in the wavefunction after the encirclement around the CI, indicatedfrom the nuclear probability distribution. On the other hand, when the initial wavefunction is placedin the upper polaritonic surface, the geometric phase significantly influences the couplings betweenpolaritonic states and therefore, the population dynamics between them. These BP effects are furtherdemonstrated through the photo-fragment angular distribution. PICI created from the quantizedradiation field has the promise to open up new possibilities to modulate photochemical reactivities.