Here µ l γν (R) are the permanent dipoles (γ = ν) and transition dipoles (γ ̸ = ν) along different directions and are usually obtained from the ab initio electronic structure calculation for the realistic molecular system. Combining Eq. 7 and Eq. 14, the light-matter coupling term ϵ • µ γν (R) in Eq. 11 can be expressed as