Vortex dynamics in Bi 2(Sr,La) 2CuO 6+ δ and Bi 2Sr 2CaCu 2O 8+ δ single crystals with columnar defects

Abstract

Vortex dynamics is studied in La-substituted Bi 2Sr 2CuO 6+ δ (Bi-2201) and Bi 2Sr 2CaCu 2O 8+ δ (Bi-2212) single crystals irradiated with 3.8 GeV 181 Ta 37+ ions through the relation between the frequency and the loss peak temperature in the temperature dependence of the imaginary part of AC magnetic susceptibility χ″. In unirradiated Bi-2201 and Bi-2212, the behavior of thermally activated flux flow or creep is observed. The Bose-glass behavior is observed at fields below the matching field B Φ in irradiated Bi-2212. On the other hand, the Bose-glass behavior is not observed in irradiated Bi-2201. This difference is due to the extremely weak coupling between pancake vortices along the c-axis in Bi-2201 even under the presence of columnar defects. The vortices in Bi-2201 irradiated with heavy ions are almost decoupled, resulting in the occurrence of thermally activated vortex creep.