PINNED VORTEX LIQUID ABOVE THE CRITICAL-POINT OF THE FIRST-ORDER MELTING TRANSITION - A CONSEQUENCE OF POINT-LIKE DISORDER

We report on a strongly pinned entangled vortex liquid above the criti cal point (CP) of the first-order melting transition in untwinned YBa2 Cu3O7-delta single crystals, Above CP, the c su;is dissipation is fini te where the in-plane dissipation is undetectable, implying large in-p lane vortex pinning in the presence of vortex cutting and recombinatio n. We demonstrate that the behavior above CP is governed by pointlike disorder. The same behavior is reproduced in twinned samples with prot on-induced point defects. [S0031-9007(97)05237-X].