Domain structure in two-dimensional lattices with randomly distributed pinning centers: Application to type-II superconductors

Abstract

We present a molecular-dynamics-based study on certain structural features of disordered two-dimensional lattices of N particles with screened Coulomb interactions which are placed on rigid substrates with Np randomly distributed Gaussian pinning centers. We find that over a wide temperature range, for Np=N and for various pinning intensities Ap, the lattice structures are typically described by domains of triangular-lattice-like regions punctuated by domains of clustered topological defects. Our calculations reveal that as Ap increases, sizable triangular-lattice-like regions coexist with increased topological defect densities. This result suggests that the particles remain correlated even at strong pinning regimes. Its implications are discussed in relation to recent experiments on heavy-ion-irradiated high-temperature superconductors and the assumptions used in various flux pinning theories of type-II superconductors.

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