Josephson-induced hysteretical behavior of vortex matter in layered BSCCO samples with columnar defects: Bose glass phase and the melting process

Abstract

We present Monte Carlo simulations of three-dimensional systems of vortex lines in the presence of random columnar defects using the Lawrence-Doniach model with BSCCO parameters. In particular, we study the structure factor and the vortex-vortex correlation length along the field (B) direction, for both intermediate and high fields. Two representative initial conditions at zero temperature (T) are used: the Abrikosov lattice and a random vortex lattice, mimicking possible configurations in a zero-field-cooled (ZFC) protocol, both characterized by smooth plane decoupling transitions (formation of pancake-like vortex structure), with exponential decay with T of the correlation length around the melting transition. The very relevant case of field-cooling (FC) from a melted configuration is also considered. In this case, as T decreases for intermediate B, the system evolves through states of an unpinned vortex lattice phase and metastable states of a phase of unpinned vortices in a Bose glass (BG) background; lastly, the system reaches a FC robust BG phase down to very low T. On the other hand, for high fields and under the ZFC protocol, the melting transition is practically concurrent with the discontinuous decoupling of planes; while, under FC, the vortex lattice decouples much before the melting transition. Indeed, we identify that the exchange between flux lines is the underlying mechanism for plane decoupling and the formation of a pancake-like vortex structure. We stress that the correspondent phase diagram B vs. T is in good agreement with previous experimental results in BSCCO.