The occurrence of superconductivity in doped SrTiO₃ at low carrier densities points to the presence of an unusually strong pairing interaction that has eluded understanding for several decades. We report experimental results showing the pressure dependence of the superconducting transition temperature, T_c, near to optimal doping that sheds light on the nature of this interaction. We find that T_c increases dramatically when the energy gap of the ferroelectric critical modes is suppressed, i.e., as the ferroelectric quantum critical point is approached in a way reminiscent to behaviour observed in magnetic counterparts. However, in contrast to the latter, the coupling of the carriers to the critical modes in ferroelectrics is predicted to be small. We present a quantitative model involving the dynamical screening of the Coulomb interaction and show that an enhancement of T_c near to a ferroelectric quantum critical point can arise due to the virtual exchange of longitudinal hybrid-polar-modes, even in the absence of a strong coupling to the transverse critical modes.

在低载流子密度下掺杂的 SrTiO ₃中出现的超导性表明存在异常强烈的配对相互作用，这几十年来一直没有被理解。我们报告的实验结果显示了超导转变温度T _c的压力依赖性，接近最佳掺杂，揭示了这种相互作用的性质。我们发现当铁电临界模式的能隙被抑制时，T _c急剧增加，即.，因为接近铁电量子临界点的方式让人想起在磁性对应物中观察到的行为。然而，与后者相反，预计载流子与铁电体中临界模式的耦合很小。我们目前涉及的动力学筛选库仑相互作用和表明的增强的定量模型Ť _Ç靠近铁电量子临界点可能由于纵向混合极性模式的虚拟交换，即使在没有强烈的耦合到横向临界模式。