Quantum paraelectric model for layered superconductors

Abstract

We consider a Hubbard-model (H) layer of charged-carrier fraction x≪1, and an rms buckling angle s≪1, that is elastically and electrically coupled to anharmonic (oxygen) dipoles in a ferroelectric Bilz-model (B) layer. We find that (a) the B-layer dipoles are driven to a paraelectric phase by H-layer zero-point fluctuations; (b) the c-axis (dipolar, optical) and H-layer (acoustic) modes are mixed by s to form ω±(q) modes; and (c) the mode exchange, enhanced by a (ω+²-ω-²)^-1~s^-1 resonant denominator, produces dynamical local carrier pairing and 2D Anderson-Morel d_x²-y²-type superconductivity, with peaks or plateaus in T_c(x).