First-order flux-lattice melting of a frustrated XY model with a [111] magnetic field

We have studied a three-dimensional isotropic Josephson-junction array in a simple cubic lattice with a magnetic field B = Phi(0)(1/3,1/3,1/3), using Monte Carlo simulation. There is a clear first-order phase transition with a latent heat of melting of about 0.11k(B)T(m) per superconducting grain at a melting temperature T-m approximate to 0.70J, where J is the intergrain coupling energy. We briefly discuss the possible relation of this transition to flux-lattice melting in high-T-c superconductors.