MONTE-CARLO STUDY OF A PERIODICALLY PINNED 2D SUPERCONDUCTOR

We show that a natural assumption on the moving mechanism of vortices in a periodically pinned, two-dimensional superconductor in the mixed state is the basis for a n-clock-like model. The pinning points are co nsidered to be centered in each unit cell of the superconducting latti ce. This property enables one to use a discrete version of the XY mode l used in the simulations focusing on the melting of the Abrikosov lat tice of vortices in a system of Josephson arrays. A Monte Carlo study performed on the corresponding Hamiltonian in a field given by a filli ng factor of f = 1/2 exhibits two phase transitions, at the temperatur es T-c1 approximate to 0.325 and T-m approximate to 0.65. The numerica l estimation of the Challa parameters for both transitions indicates t heir continuous nature. The physical meaning of the lower transition i s the expulsion of the magnetic field from the superconducting system, i.e. the Meissner effect. The physical equivalent of the upper transi tion is the melting of the pinned vortex lattice.