As shown in Fig. , the transition dipoles of the trans isomer (with CNNC dihedral angle being ∼ 180 • ) are zero in all directions due to the symmetry of the trans isomer, while the transition dipole of the cis isomer has finite value (∼ 0.8 Debye) in the Y direction. Hence, the |e⟩ state is a dark state at the trans configuration, while is a bright state at the cis configuration. This is also the reason why we chose the cis isomer as the initial configuration to perform the dynamics, as mentioned in Sec. 4.1. In addition, we note that near the Franck-Condon region, the permanent dipoles are much smaller than the transition dipole along the Y-axis. In contrast, the permanent dipoles are much larger than the transition dipole along the Z-axis. Moreover, compared to the dipoles along the Y-and Z-axes, the dipoles along the X-axis are much smaller (< 0.7 Debye). As a result, we will only perform the ab-initio molecular cavity QED simulations with the field polarized along the Y-and Z-axes in this work.