Superconducting Current in Mesa Structures with Interlayer of Strontium Iridate, a Material Having Strong Spin-Orbit Interaction

We report on observation of superconducting current and AC Josephson effect in mesa-heterostructures with the interfaces comprised spin-singlet superconducting electrodes, coupled by a barrier made from strontium iridate, a material with the strong spin-orbit interaction. The superconducting critical current density was jC ≈ 0.3 A/cm2 at T = 4.2 K for mesa-heterostructures with d = 7 nm and jC ≈ 4 A/cm2 for d = 5 nm. The zero-bias conductance peak has been observed due to low energy states originated at Sr2IrO4/YBa2Cu3Ox interface. Under influence of weak magnetic field the critical current IC(H) dependences showed Fraunhofer-like pattern indicating absence of pinholes, supported also by oscillating with microwave power Shapiro steps. Fiske resonance steps with voltage positions deviated from the ordinary ones were registered for mesas with d = 5 nm.