Narrow Results

Using molecular dynamic simulations for the melting transition of a flux line lattice(FLL) with point disordered pinnings, thermal fluctuations and magnetic interactions between pancake vortices, we study the disorder-driven melting transition from a disentangled and ordered Bragg glass (BG) to an entangled amorphous vortex glass (VG) or a vortex liquid (VL) in the pinning strength-temperature phase diagram. A portion of the BG region is found to be sandwiched in between the VG phase at lower temperatures and VL phase at higher temperatures, exhibiting inverse melting behavior observed recently on BSCCO crystals.

We study translational correlations of the vortex center of mass positions of the Abrikosov flux line lattice in superconducting samples of finite thickness L (along the direction of flux lines). The Larkin correlation lengths for the center of mass mode of the flux lines in the presence of point and correlated disorder are computed, and we find that in the case of point disorder the average (i.e. center of mass) position of flux lines maintains positional order on length scales which scale like in 2+1 dimensions. On still longer length scales, however, we find using a replica Gaussian variational approach that center of mass correlations cross over to a power law growth of the form r_⊥/L, which should be observable in superconducting thin films.