Electrodynamics of Nearly-Ferroelectric Superconductors

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We report here the frequency-dependent optical response of a nearly ferroelectric superconductor (NFE-SC), like NaₓWO₃, or n-SrTiO₃. From ω=0, up to a critical frequency ωc₁, Meissner-like field extinction occurs as in a usual superconductor. In the "anomalous" region ωc₁<ω<ωTO (the TO frequency of the NFE) the field propagates as in a dielectric. For ω>ωTO Meissner damping recurrs, then at higher ω, dielectriclike propagation is found. New optical anomalies (peaks in transmission) are predicted for a film of NFE-SC below the soft mode frequency ωTO. These effects are due to including the contribution of the NFE displacement current in the solution of the coupled Maxwell, lattice and London equations. Quantitative calculations are given for the NFE-SC n-SrTiO₃ to illustrate this.