Observation of the second harmonic in superconducting current-phase relation of Nb/Au/(001)YBa ₂ Cu ₃ O _<i>x</i> heterojunctions

Abstract

The superconducting current-phase relation (CPR) of Nb/Au/(001)YBa2Cu3Ox\nheterojunctions prepared on epitaxial c-axis oriented YBa2Cu3Ox thin films has\nbeen measured in a single-junction interferometer. For the first time, the\nsecond harmonic of the CPR of such junctions has been observed. The appearance\nof the second harmonic and the relative sign of the first and second harmonics\nof the CPR can be explained assuming, that the macroscopic pairing symmetry of\nour YBa2Cu3Ox thin films is of the d+s type\n