Ginzburg-Landau Theory of Vortex Phase Diagram in Layered Type II Superconductor

Recent theoretical understanding of the vortex phase diagram in real layered type II superconductors is briefly described in both cases with fields perpendicular (B \parallel c) and parallel (B \perp c) to the superconducting layers. The description is based on a high field approximation of the Lawrence-Doniach model and on a vortex-glass ordering in each case. It is argued that, generically, the familiar thermal first order transition at B_m(T) occurs between the vortex liquid region and the so-called vortex slush region, and that, in systems with stronger fluctuation, most of the thermal first order line is covered by the first order melting of the Bragg-glass phase. Recent observations in YBCO in B \parallel c of the vortex slush region and of the lower critical point of B_m(T) are understood in this way. Based on the same scenario, recent resistivity data in YBCO and BSCCO, suggestive of the phase diagram in B \perp c, are explained.