Superconducting heterostructure with barrier with strong spin-orbit interaction

Abstract

We report on observation of superconducting current and AC Josephson effect in mesa-heterostructures with spin-singlet superconducting electrodes, interlayered by a barrier material with strong spin-orbit interaction. The mesa-heterostructures were Nb/Au/Sr2IrO4/YBa2Cu3Ox with d=5 nm and 7 nm thick interlayer of strontium iridate Sr2IrO4, which is known as a canted antiferromagnetic insulator with a weak magnetic moment from Ir atoms and with spin-orbit interaction energy ESO ~0.4 eV. The superconducting critical current density was jC ≈0.3 A/cm2 at T=4.2 K for mesa-heterostructures with d=7 nm and a few times higher 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.