Vortex-glass superconductivity in a typical weak-link YBa2Cu3O7-y/SiO2 system.

Abstract

Vortex-glass superconductivity is studied in an extreme weak-link system of ${\mathrm{YBa}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{7\mathrm{\ensuremath{-}}\mathit{y}}$/${\mathrm{SiO}}_{2}$ composite by measuring the I-V curve in a series 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 positive to negative are observed and the equilibrium phase boundary line between the normal and superconducting phases in the H-T plane is obtained. In the magnetic field lower than 135 Oe, the system shows a magnetic-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 glass in the weak-link network system is different from that in the superconducting single-crystal system.