Observation of ZBCP Above T_C at Au/Y_1Ba_2Cu_3O_(7-δ) Heterostructure with a Nano Hole: A Possible Evidence for the Cooper Pairs above T_C

摘要

Fabrication of a nanojunction by making a nano-hole on PMMA layer deposited in between Au and Y_1Ba_2 Cu_3O_(7-δ) (YBCO) films is reported. We have measured the current-voltage characteristics across Au/YBCO nanojunction at different temperatures and studied Andreev Reflection (AR) phenomena. The presence of Zero Bias Conductance Peak (ZBCP) due to AR, which is considered to be the well-known feature of d-wave superconductors, has been noticed at temperatures below and above the transition temperature (T_C ～ 87 K) up to 130 K. The result obtained indicates the possible- existence of the phase-incoherent Cooper pairs above T_C for Au/YBCO.