P. Santhanam

Interacting loop-current model of superconducting networks

We review our recent approximation scheme to calculate the normal-superconducting phase boundary, Tc(H), of a superconducting wire network in a magnetic field in terms of interacting loop currents. The theory is based on the London approximation of the linearized Ginzburg-Landau equation. An approximate general formula is derived for any two-dimensional space-filling lattice comprising tiles of two shapes. We provide many examples illustrating the use of this method with a particular emphasis on the fluxoid distribution. In addition to periodic lattices, we also discuss quasiperiodic lattices and fractal Sierpinski gaskets.

Critical behavior of periodic networks containing tiles with irrational ratio of areas

Abstract We review our recent measurements of the suoerconducting-normal transition boundary, Hc(H), of two new two-dimensional periodic networks. Each network is a mixture of squares and equilateral triangles in the number ratio 1:2. In both cases we observe maxima in Tc(H) with one major period, which corresponds to an area Ap = Asq + 2Atr. In this paper we discuss some details of the solutions of London loop equations. The behavior of these networks in the continuum limit (for small applied fields) is also discussed.