Vortex solid state in YBa2Cu3O7-δ twinned crystals -: art. no. 052511

We report on the scaling of transport properties around the vortex melting in YBa2Cu3O7-delta oriented-twin single crystals in applied magnetic fields between 1 T and 18 T. We find that for the whole measured field range the linear resistivity scales as rho (t, theta)similar tot(sy) F+/- (sin(theta )t(-sx)), with t= \T-T-BG\ and theta the angle between planar defects and the magnetic field. The scaling is valid only for angles where the transition temperature T-BG(theta) shows a cusp. The critical exponents sx and sy are in agreement with the values predicted by Lidmar and Wallin [Europhys. Lett. 47, 494 (1999)] only at magnetic fields below 4 T. A change in the value of sx from sx= 1 +/-0.2 to sx= 3 +/-0.2 at around H(cr)approximate to4 T when the magnetic field is increased is responsible for changes in the shape of the T-BG(theta) curve and in the dependence of the linear dissipation on temperature and angle. The results strongly suggest the existence of a different vortex glassy phase in twinned crystals compared to the Bose-glass state found in samples with linear defects.