Many of the properties of SrTiO3 (STO), including superconductivity, are still mysterious more than a half-century after its discovery. One can gain new insights into superconducting semiconductors like STO by comparing it with a close relative, KTaO3 (KTO). The recent discovery of superconductivity at KTO interfaces and surfaces offers the possibility of “stereoscopic” insight into superconductivity, and the possible role of incipient ferroelectricity, strong spin-orbit coupling, and structural phase transitions in mediating pairing interactions.
Why do KTO(111) and KTO(110) heterostructures exhibit superconductivity while KTO(100) does not? Is KTO superconductivity associated with a near-surface structural phase transition? Does KTO exhibit signatures of electron pairing outside the superconducting regime? What is the role of spin-orbit coupling? The mesoscopic transport techniques developed for STO-based heterostructures provide a clear roadmap for experiments with KTO-based heterostructures.