First-order melting and dynamics of flux lines in a model forYBa2Cu3O7−δ

Seungoh Ryu, D. Stroud
1996 Physical Review B (Condensed Matter)  
We have studied the statics and dynamics of flux lines in a model for YBCO, using both Monte Carlo simulations and Langevin dynamics. For a clean system, both approaches yield the same melting curve, which is found to be weakly first order with a heat of fusion of about $0.02 k_BT_m$ per vortex pancake at a field of $50 {\rm kG}.$ The time averaged magnetic field distribution experienced by a fixed spin is found to undergo a qualitative change at freezing, in agreement with NMR and $\mu {\rm
more » ... MR and $\mu {\rm SR}$ experiments. Melting in the clean system is accompanied by a proliferation of free disclinations which show a clear B-dependent 3D-2D crossover from long disclination lines parallel to the c-axis at low fields, to 2D "pancake" disclinations at higher fields. Strong point pins produce a logarithmical $\ln t$ relaxation which results from slow annealing out of disclinations in disordered samples.
doi:10.1103/physrevb.54.1320 pmid:9985405 fatcat:wihkx3l2wjbv5oqvtq7k6gnkqa