Robust Superconductivity at the KTaO3(111) Interfaces

Two-dimensional (2D) superconductivity is a fertile landscape for novel and exotic quantum phenomena. Highly crystalline 2D superconductors have allowed observation of intrinsic quantum phenomena, such as violation of paramagnetic Pauli limit, quantum metallic state, and quantum Griffiths phase. Spin-orbit coupling (SOC) in crystalline 2D superconductors leads to a robust superconducting state, surviving anomalous applied magnetic fields. We grew high quality, epitaxial KTaO₃ interfaces, using an oxide molecular beam epitaxy. The cross-section high-angle annular dark-field imaging in scanning transmission electron microscopy shows an atomically abrupt interface. The sheet resistance with temperature demosntrates a a metallic behavior with carrier mobility as high as∼300 cm²/V.s. We observe an anisotropic superconductivity with enhanced in-plane critical field, exceeding the Pauli limit. I will discuss the nature of superconductivity in the context of electronic structure, orbital character, and spin texture at the KTaO3 (111) interfaces. The results point to new opportunities to enhance superconducting critical fields in crystalline 2D superconductors with strong SOC.