Size dependence and mesoscopic effect of YBa2Cu3O7-delta/La0.67Sr0.33MnO3 junctions

The size dependence of transport properties is studied in YBa2Cu3O7-delta/L a0.67Sr0.33MnO3 (YBCO/LSMO) junctions. When the junction size is 40 x 30 mu m(2), a large zero-bias conductance peak originated from d-wave pairing sym metry has clearly been observed. However, as the junction size becomes smal ler (15 x 15 mum(2)), the conductance spectra are drastically changed. The large peak becomes broader, and a small zero-bias peak with a pair of dips whose energy levels are symmetric with respect to zero-bias appears only be low 6 K. The features peculiar to the small junction reflect the presence o f the phase coherent transport due to the mesoscopic size of effective junc tion area. (C) 2001 Elsevier Science B.V. All rights reserved.