Superconductivity mediated by polar modes in ferroelectric metals

The superconductivity in doped SrTiO3 at low carrier densities is attributed to an unusually strong pairing interaction. This study investigates the pressure dependence of the superconducting transition temperature (Tc) near optimal doping to understand this interaction. Tc increases dramatically when the ferroelectric critical modes' energy gap is suppressed, similar to magnetic counterparts. However, unlike magnetic systems, the coupling to critical modes in ferroelectrics is predicted to be weak. A quantitative model involving Coulomb interaction's dynamical screening shows that Tc enhancement near a ferroelectric quantum critical point is possible due to the virtual exchange of longitudinal hybrid-polar-modes, even without strong coupling to transverse critical modes.

C. Enderlein, J. Ferreira de Oliveira, D. A. Tompsett, E. Baggio Saitovitch, S. S. Saxena, G. G. Lonzarich, S. E. Rowley