Bose-glass melting in the cubic (K,Ba)BiO3 high-Tc oxide with columnar defects

The Bose-glass transition in the fully isotropic (K,Ba)BiO3 superconductor with columnar defects produced by irradiation with 7.2 GeV Ta ions was studied by transport and nonlinear susceptibility measurements. For fields smaller than the dose equivalent field B-phi, the Bose-glass transition line H-BG(T) shifts progressively upwards with increasing dose, dH(BG)/dT similar to 1+alpha B-phi(1/2). The critical exponents have been deduced from the scaling properties of the transport measurements; we obtain z=5.3+/-0.3 and nu=1.1+/-0.2. For tilted magnetic fields, the transition temperature scales as T-BG(0)-T-BG(theta)similar to\sin(theta)\(1/nu), as recently suggested by Lidmar and Wallin.