Persistent critical current of YBa_2Cu_3O_(7-δ) nanowires

摘要

C-axis oriented YBa_2Cu_3O_(7-δ) (YBCO) nanowires have been fabricated so as to connect two c-axis oriented semi-ring-shaped YBCO thin films along the c-axis direction. This allows the characterization of high-T_c nanowires with the electrodes being of the same material. Four different lengths of the nanowire arrays were characterized. When the YBCO nanowires were narrower than 100 run, their persistent critical current revealed an anomalous temperature dependence. The narrow YBCO nanowires behave like superconductor/semiconductor/superconductor junctions with a universal critical current density J_C(T) ∝ (T_c - T)~(3/2) at low temperatures. Above a certain temperature T~*, the flow of the supercurrent is controlled by thermally activated phase-slip events, with J_C(T) following a power-law dependence J_c ∝ (T_c -T)~(α>3/2).