The 3D-like behavior in the ultrathin epitaxial YBa2Cu3O7-x films

The current-voltage (IV) characteristics in ultrathin 30 Å thick epitaxial YBa2Cu3O7-x films have bee investigated at high magnetic fields up to 13T. The analysis of IV-curves in the double-logarithmic scale undoubtedly shows the features of 3D-glass behavior, i.e. the linear resistance RL undergoes the sharp transition at some finite Tp(H) at which the curvature of logV(log(I)) changes from positive to negative one. The seeming contradiction with the previously published results on ultrathin films, where 2D behavior was observed, can be explained by the fact, that the ultrathin films used in our experiments are of high quality and posses very high values of critical currents about 106 A/cm2