  After almost twenty years of intense work on the celebrated LaAlO3/SrTiO3
system, the recent discovery of a superconducting two-dimensional electron
gases (2-DEG) in (111)-oriented KTaO3-based heterostructures injects new
momentum to the field of oxides interfaces. However, while both interfaces
share common properties, experiments also suggest important differences between
the two systems. Here, we report gate tunable superconductivity in 2-DEGs
generated at the surface of a (111)-oriented KTaO3 crystal by the simple
sputtering of a thin Al layer. We use microwave transport to show that
(111)-KTaO3 2-DEGs exhibit a node-less superconducting order parameter with a
gap value significantly larger than expected within a simple BCS weak-coupling
limit model. Consistent with the two-dimensional nature of superconductivity,
we evidence a well-defined Berezinsky-Kosterlitz-Thouless type of transition,
which was not reported on SrTiO3-based interfaces. Our finding offers
innovative perspectives for fundamental science but also for device
applications in a variety of fields such as spin-orbitronics and topological
electronics.
