In the very strong coupling limit (e.g, an infinite light-matter coupling), the overlap m j |n i approaches to zero, effectively eliminating all diabatic electronic couplings V ij (R). As such, the polariton Hamiltonian becomes Ĥpl = i,n i V i (R) + (n i + 1 2 )hω c |µ i , n i n i , µ i |, where the light and matter are effectively decoupled. This agrees with the recent theoretical analysis of atomic QED systems under the deep strong coupling limit. It also indicates that, as the light-matter coupling goes large, the polariton state