Superconducting KTaO3 2DEGs – SURIKAT

The first months of 2021 have seen the discovery of a new family of superconducting two-dimensional electron gases (2DEGs) at oxide interfaces based on KTaO3 (KTO). Importantly, the TC and spin-orbit coupling (SOC) in these 2DEGs are both 5-10 times higher than in their SrTiO3 counterparts that have been intensely investigated since their discovery in 2004. Our consortium has recently obtained important results on this new system, albeit with a growth method advantageous for device nanofabrication. Equipped with these preliminary results, SURIKAT ambitions to explore the fundamental properties of KTO 2DEGs and to realize superconducting devices. We will study the superconducting phase of the 2DEGs, including the role of the band structure and crystal orientation on superconductivity, the nature of the superconducting state (single gap vs multigap) and the symmetry of the order(s) parameter(s). This knowledge will serve as a basis to understand the origin of superconductivity in KTO 2DEGs and in quantum para-electrics in general. We will also explore the relationship between Rashba SOC and superconductivity in the context of topological superconducting phases. We will then investigate the coupling between superconductivity and ferroelectricity in 2DEGs formed in Nb-substituted KTO substrates (KTN) both from theoretical and experimental perspectives. Based on results obtained in ferroelectric phases derived from STO, we anticipate an enhancement of TC beyond 4 K. Finally, we will fabricate field-effect devices in KTO 2DEGs such as Josephson junctions, SQUIDs and one-dimensional nanowires to use them to gain further insight into the superconducting state, by testing recent predictions in multigap s± wave superconductors and ferroelectric superconductors, and looking for topological states as well.