Vortex solid state in YBa2Cu3O7-δ twinned crystals

Abstract

We report on the scaling of transport properties around the vortex melting in YBa2Cu3O7−δ 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 ρ(t,θ)∼tsyF±(sin(θ)t−sx), with t=|T−TBG| and θ the angle between planar defects and the magnetic field. The scaling is valid only for angles where the transition temperature TBG(θ) 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 Hcr≈4T when the magnetic field is increased is responsible for changes in the shape of the TBG(θ) 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.