Ferroelectric Enhancement of Superconductivity in Incipient Ferroelectrics

A combination of broken inversion symmetry and spin-orbit coupling gives rise to a wide range of exotic superconducting states, such as mixed-parity superconductivity and superconducting diode effect which can be harnessed towards unconvensional computation. Incipient ferroelectrics e.g., SrTiO₃, KTaO₃, EuTiO₃, and PbTe are near a polar instability. The emergence of superconductivity has been reported in some of these incipient ferroelectrics upon doping. Many unconventional superconductors, such as the cuprates, pnictides, and heavy fermion systems, occur in close proximity to magnetic fluctuations or magnetic orders, suggesting that these are important ingredients in the superconductivity in these materials. Here, ferroelectricity and superconductivity could be connected or accidental neighbors. Furthermore, the intersection of superconductivity and topologically nontrivial states is a fertile landscape for exciting quantum phenomena, including non-abelian excitations. Topologically nontrivial states have been reported in some of these polar superconductors. First, I will introduce the emergence of superconductivity and its interplay with ferroelectricity in tuned SrTiO₃ thin films. The ferroelectric films reveal a doubling in the critical temperature of superconductivity. Next, I will present our recent results on the emergence of 2D superconductivity in KTaO₃(111) interfaces and doped SnTe. I will discuss the nature of superconductivity in the context of electronic structure, orbital character, and spin texture in thes materials systems.