VORTEX-GLASS SUPERCONDUCTIVITY IN A TYPICAL WEAK-LINK YBA2CU3O7-Y SIO2 SYSTEM/

Vortex-glass superconductivity is studied in an extreme weak-link syst em of YBa1Cu3O7-y/SiO2 composite by measuring the I- V curve in a seri es of low magnetic fields. The feature of the vortex-glass transition, i.e., the changes of the curvature of the I- V curves from the positi ve to negative are observed and the equilibrium phase boundary line be tween the normal and superconducting phases in the H- T plane is obtai ned. In the magnetic field lower than 135 Oe, the system shows a magne tic-field-independent scaling behavior; but a magnetic-field-dependent scaling behavior is observed in higher fields. A relatively low value of the dynamical exponent z suggests that the dynamics of vortex glas s in the weak-link network system is different from that in the superc onducting single-crystal system.