Memory Effects in a Superconducting Y-Ba-Cu-O Single Crystal: A Similarity to Spin-Glasses

Abstract

We report on memory effects observed in the time dependence of the magnetization $M(T, H)$ of a superconducting Y-Ba-Cu-O single crystal. As in spin-glasses, the decay rate $S=\frac{\mathrm{dM}}{d\mathrm{ln}t}$ is not uniquely determined. It exhibits a characteristic change at time $t$ equal to the waiting time ${t}_{w}$ during which the specimen was kept at a given temperature $T<{T}_{c}$ and magnetic field $H$ before a field perturbation $\ensuremath{\Delta}H$ is applied at time $t=0$. This phenomenon, seen for the first time in a superconductor, reveals the glassy nature of the superconducting state in the high-${T}_{c}$ oxides.