Phase Diagram of Vortices in High-T_c Superconductors with a Melting Line in the deep H_{c2} Region
arXiv:0807.2757 · doi:10.1103/PhysRevB.79.014512
Abstract
We use a simple elastic Hamiltonian for the vortex lattice in a weak impurity background which includes defects in the form of integer-valued fields to calculate the free energy of a vortex lattice in the deep H_{c2} region. The phase diagram in this regime is obtained by applying the variational approach of M{é}zard and Parisi developed for random manifolds. We find a first-order line between the Bragg-glass and vortex-glass phase as a continuation of the melting line. In the liquid phase, we obtain an almost vertical third-order glass transition line near the critical temperature in the H-T plane. Furthermore, we find an almost vertical second-order phase transition line in the Bragg-glass as well as the vortex-glass phases which crosses the first-order Bragg-glass, vortex-glass transition line. We calculate the jump of the temperature derivate of the induction field across this second-order line as well as the entropy and magnetic field jumps across the first-order line.
19 pages, 5 figures, a discussion is added at the end of section VI relating our results with the results of Refs. 4, 10, typos corrected, version published in PRB
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