In the Supporting Information, we further provide the Polariton PESs obtained from Quantum Optics Models, including the commonly used Jaynes-Cummings model and Quantum Rabi Model. The accuracy and validity of commonly used model systems need to be carefully assessed before adapting them to the field of molecular cavity QED. Unfortunately, these well-established approximations in the atomic cavity QED can explicitly break down in the molecular cavity QED, as shown in Fig. . Thus, one needs to use the most rigorous Hamiltonian to describe the light-matter interactions and try to avoid unnecessary approximations. Accordingly, one should use a rigorous QED Hamiltonian (such as Eq. 2) to describe the light-matter interactions and avoid unnecessary approximations.