Evolution of self-organized bulk vortex structure induced by hole doping in the high-temperature superconductorYBa2Cu3O7−δ

Abstract

Studies of the persistent current relaxation of ${\text{YBa}}_{2}{\text{Cu}}_{3}{\text{O}}_{7\ensuremath{-}\ensuremath{\delta}}$ ring-shaped thin films as a function of oxygen concentration (with 24 increments in $\ensuremath{\delta}$ every $\ensuremath{\sim}0.021$, over a range between 0.03 and 0.55) allowed us to construct the $(\ensuremath{\mu},\ensuremath{\delta})$ phase diagram where the exponent $\ensuremath{\mu}$ characterizes the pinning ability and the nature of the vortex structure. The reduction of the hole-doping level (an increase in $\ensuremath{\delta}$) transforms the vortex structure from quasi-lattice into a glass and subsequently into a pinned liquid phase. These vortex phases self-organize and produce relaxation plateaus in regions between steplike changes in the dependence of relaxation kinetics on hole doping.