Many-body mechanism of quantum paraelectricity and THz-driven transient ferroelectricity

We show that quantum paraelectricity can be described by the transverse-field Ising model. Elementary optical-mode excitations are fractionalized into Jordan-Wigner fermions. An electric field couples only to finite-k modes determined by proximity to the critical point, explaining the finite-k anomalies observed in diffuse x-ray scattering [1], in coupling to acoustic phonons, and as static polarization nanodomains [2]. Transient ferroelectric dynamics observed in THz-driven quantum paraelectrics [3] involve a slow relaxation of THz-driven Bogolyubov rotation superimposed with oscillations of the small-k modes. This process cannot be described by single-particle quantum or classical models due to the interplay between classical and quantum coherence in an interacting many-body system.