We have studied a three-dimensional isotropic Josephson-junction array in a simple cubic lattice with a magnetic field $\mathrm{B}={\Phi }_0(\frac{1}{3}, \frac{1}{3}, \frac{1}{3})$, 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 $T_m\approx 0.70J$, 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.

• Received 24 June 1996

DOI:https://doi.org/10.1103/PhysRevB.54.14978