-based 2D gas.

The achievement of high-quality epitaxial interfaces involving transition metal oxides offers a unique opportunity to design artificial materials that host novel electronic phases.  After fifteen years of dedicated research on SrTiO₃ -based interfaces [1], the recent discovery of a superconducting 2-DEG) in (111)-oriented KTaO₃-based heterostructures injected new momentum into the realm of oxide interfaces [2,3]. In this system, the superconducting T_c can exceed 2K, nearly an order of magnitude higher than that observed in SrTiO₃-based interfaces. Additionally, the increased mass of Ta compared to Ti leads to significantly enhanced spin-orbit effects, as recently demonstrated [4,5]. Consequently, KTaO₃-based 2-DEGs have the potential to enable the realization of topological superconducting phases—a concept originally proposed for SrTiO₃-based 2-DEGs but hitherto unattainable due to the limitations of the relevant energy scales. In this talk, I will present dc and microwave transport experiments on gate tunable superconducting 2-DEGs formed at the (111)-oriented AlOx/KTaO₃ interface. The temperature dependence of the superfluid stiffness, extracted from the microwave response of the 2-DEG, is found to be consistent with a node-less superconducting order parameter having a gap value larger than expected within a simple BCS weak-coupling limit model (Δ₀/k_BT_c= 2.3) [6]. Moreover, the superconducting transition follows the Berezinskii-Kosterlitz-Thouless scenario, a phenomenon not previously reported in SrTiO₃-based interfaces. In addition, I will also present recent measurements of the superconducting gap obtained via tunneling spectroscopy in Au/AlOx/(111)-KTaO₃  planar junctions and discuss its temperature dependence and evolution under a perpendicular magnetic field. Finally, I will provide perspectives on the realization of superconducting devices

References

[1] A. Caviglia et al., Nature 456, 624–627 (2008).[2] Liu, C. et al. Science 371, 716–721 (2021).

[3] Chen, Z. et al. Science 372, 721–724 (2021).

[4] Vicente-Arche, L. M. et al. Adv. Mater. 2102102 (2021).

[5] S. Varotto, et al. Nature Commun. 13, 6165 (2022).

[6] S. Mallik et al. Nature Commun. 13, 4625 (2022)