The importance of initial states in polariton simulation

Abstract

Nonadiabatic simulation methods are indispensable tools to investigate the dynamical processes, including the polariton formed by the hybridisation of molecule and photon. The direct product state, say ( ), is a convenient choice to start the simulation, with and denoting the molecular and photon ground state, respectively. Here, by using exact quantum dynamics simulation, we show that the LiF molecule in a cavity can become self-excited if the simulation starts with the direct product state , leading to a finite probability to dissociate. The physical picture behind the product state simulation is that we turn on the light-matter interaction suddenly, which causes the system to occupy the high energy states that are directly coupled with the initial state even though the total energy of the whole system is conserved. Through a time-dependent light-matter interaction model, we show that the self-excited state will disappear if the molecule moves into the cavity more slowly, i.e. adiabatically. Our results and model highlight the importance of the initial state of polariton simulation and the direct product state is unfeasible to be the initial state to investigate the dynamics of polariton, which provides new insights into the theoretical investigation of polariton dynamics.