Vortex matter freezing in Bi$_{2}$Sr$_{2}$CaCu$_{2}$O$_{8}$ samples with a very dense distribution of columnar defects

摘要

We show that the dynamical freezing of vortex structures nucleated at diluteddensities in Bi$_{2}$Sr$_{2}$CaCu$_{2}$O$_{8}$ samples with a densedistribution of columnar defects, $B \sim 10^{-2} B_{\Phi}$ with$B_{\Phi}=5$\,kG, results in configurations with liquid-like correlations. Wepropose a freezing model considering a relaxation dynamics dominated bydouble-kink excitations driven by the local stresses obtained directly fromexperimental images. With this model we estimate the relaxation barrier and thefreezing temperature. We argue that the low-field frozen vortex structuresnucleated in a dense distribution of columnar defects thus correspond to anout-of-equilibrium non-entangled liquid with strongly reduced mobility ratherthan to a snapshot of a metastable state with divergent activation barriers asfor instance expected for the Bose-glass phase at equilibrium.