Electrodynamics of ferroelectric films with negative capacitance

We construct a comprehensive theory of the electrodynamic response of ferroelectric ultra-thin films containing periodic domain textures (PDT) with 180{\deg} polarization-oriented domains. The focal point of the theory is the negative-capacitance phenomenon which naturally arises from the depolarization field induced by PDT. We derive frequency-dependent dielectric permittivity related to the PDT dynamics across the entire frequency range. We find the resonance mode of domain oscillations in the THz spectral band and the singular points in the phase of the reflected THz beam that are intimately related to the negative capacitance. Our findings provide a platform for the THz negative capacitance-based optics of ferroelectric films and for engineering the epsilon-near-zero plasmonic THz metamaterials.