Transport and noise properties of high T-c bicrystal junctions

Transport properties of YBa2Cu3O7-x, bicrystal junctions are studied from t he relationship between the critical current I-c and the resistance R of th e junction. The relation is obtained when misorientation angle of the junct ion is changed from 24 to 36.8 degrees. The experimental result can be well explained when two effects are taken into account in the tunnelling of ele ctrons, i.e. resonant tunnelling of quasiparticles via localized states in an insulating barrier and d-wave symmetry of the superconducting order para meter. Low frequency 1/f noise of the junction is also measured, and the fl uctuations of I-c and R are obtained as a function of junction parameters. A simple model of the barrier height fluctuation due to the capture and emi ssion of electrons in the localized states can quantitatively explain the e xperimental results. The present model can consistently explain both the tr ansport and noise characteristics of the bicrystal junction.