Evidence for diverging barriers in the disordered vortex solid in the (K, Ba)BiO3 superconducting oxide - art. no. 167002

Vortex dynamics has been investigated in the cubic (K, Ba)BiO3 superconduct or using ac susceptibility measurements on a large frequency range (0.03 Hz < <omega> < 60 kHz). Power law diverging barriers have been obtained on bo th sides of the order-disorder transition line. The <mu> exponent remains c lose to 5/2 (elastic creep value) in some part of the disordered phase and finally decreases at high temperature and/or high field, in good agreement with the recent plastic collective creep theory [J. Kierfeld, H. Nordborg, and V. M. Vinokur, Phys. Rev. Lett., 85, 4948 (2000)].