Cavity molecular dynamics simulations of liquid water under vibrational ultrastrong coupling

We simulate vibrational strong (VSC) and ultrastrong coupling (V-USC) for liquid water with classical molecular dynamics simulations. When the cavity modes are resonantly coupled to the O-H stretch mode of liquid water, the infrared spectrum shows asymmetric Rabi splitting. The lower polariton (LP) may be suppressed or enhanced relative to the upper polariton (UP) depending on the frequency of the cavity mode. Moreover, although the static properties and the translational diffusion of water are not changed under VSC or V-USC, we do find the modification of the orientational autocorrelation function of H${}_2$O molecules especially under V-USC, which could play a role in ground-state chemistry.