Bose-glass transition in Pb-substituted Bi-2212 single crystals containing parallel tilted columnar defects

Abstract

We have studied the effect of tilted columnar defects (CD’s) on vortex dynamics in Bi 1.8Pb 0.2Sr 2CaCu 2O 8+ δ . Single crystals were irradiated by high-energy heavy-ions either parallel or along the direction inclined at θ irr=45° relative to the crystals c-axis. The angular dependence of the resistance R( ψ) exhibits an usual directional effect, in the vortex solid state and for T⩾40 K, when a magnetic field is aligned to the CD’s for both cases. In the case of inclined linear defects, an anomalous clear minimum centred along the perpendicular direction to the CD’s is observed. The melting transition for magnetic fields applied in the direction parallel to CD’s and over a wide range of the filling factor ( f< H/ B φ ) from f=0.026 to 0.9, is analysed by I– V scaling. Both samples under examination show a 3D Bose-glass (BG) transition with the same critical exponents ( z ′=5.27±0.05 and ν ′=1.04±0.06). These results supports the persistence of a BG-to-liquid transition at T BG( B) in the case of inclined defects. The R( ψ) curves measured at low temperatures in the case of inclined CD’s reveal two main features. first, the dip centred at the tracks at high-temperature shifts away from the CD’s toward the c-axis. Second, the persistence of the directional pinning at low temperatures, in contrast to previous experiments at low temperatures on Bi-2212 single crystals showing isotropic pinning.