Resonant current steps in Josephson structures with a layer from a material with strong spin–orbit interaction

The microwave and magnetic parameters of Josephson Nb/Au/Sr$_{2}$IrO$_{4}$/YBa$_{2}$Cu$_{3}$O$_{x}$ mesastructures with a layer of Sr$_{2}$IrO$_{4}$, a material representing a Mott antiferromagnetic insulator with a high spin–orbit interaction energy $E_{\mathrm{SO}}\sim$ 0.4 eV, were studied. Shapiro steps, oscillating with radiation power, appeared under monochromatic electromagnetic radiation confirm the Josephson properties of these structures. In the presence of a weak magnetic field $H<$ 15 Oe, the voltage–current characteristics (VCCs) had resonant current steps at voltages $V_{n}$, which were inversely proportional to the size $L$ of structures in plane. Polarity reversal in the electrical current $I$ led to asymmetry in the arrangement of resonant current steps. At a specified magnetic field $H$, the voltage $V_{n}$ remained constant, and the amplitudes of resonant current steps nonmonotonically changed.