Intrinsic Josephson properties in Pb_1-ySr₂Y_1-xCa_xCu_2+yO_7+δ epitaxial films

We report the first observation of intrinsic Josephson junction (IJJ) characteristics in the Pb_1-ySr₂Y_1-xCa_xCu_2+yO_7+δ (Pb1212) epitaxial film. Pb1212 epitaxial film has been grown on SrTiO₃ (100) substrates by a two-step growth technique. A small mesa structure (S = 4μm²) has been fabricated on a film surface using a standard photolithography and an Ar ion milling technique. The superconducting transition temperature of the IJJ is 43 K. At 4.2 K, the value of J_c (the critical current density) is 2.2 kA/cm². The depth of the hysteresis defined as α = (J_c+J_r)/ J_c is 0.89, where J_r is the return current density. The temperature dependence of J_c shows good agreement with Ambegaokar-Baratoff theory