BOSE-GLASS MELTING IN YBACUO CRYSTALS WITH CORRELATED DISORDER

We report a sharp melting transition of the Bose glass in YBaCuO crystals with columnar defects installed by the irradiation with 1 GeV Au ions. The melting B(BG)(T) is tracked at low fields by the irreversibility line, which undergoes a remarkably abrupt crossover at a field B(cr) for the vortices aligned with columns along the c axis. Below B(cr), the upward curvature of B(BG) is-proportional-to (1 - T/T(c))alpha increases with the pin density (the exponent alpha grows from the clean value of approximately 4/3 to approximately 2 at the highest irradiation doses), in quantitative agreement with the theory of melting in the presence of correlated disorder. Above B(cr), the linear in T irreversibility line is consistent with a transition into a (super)entangled vortex liquid.