Abstract
We report on the observation of a change in the field dependence of the critical current density of superlattices at a characteristic magnetic field . This change shows up as an abrupt transition when analyzing the current-voltage ( ) characteristics in the framework of the vortex glass and collective flux creep theories. This behavior can be traced back to a sudden reduction in the collective pinning energy above , and may reflect a softening transition of the vortex lines in the vortex solid. is very similar to the characteristic field in the vortex liquid phase, which we interpreted to be due to entanglement.
- Received 14 December 1994
DOI:https://doi.org/10.1103/PhysRevLett.74.3041
©1995 American Physical Society