Localization Effect in a 2D Superconducting Network without Disorder

The superconducting properties of a two-dimensional superconducting wire network with a new geometry have been measured as a function of the external magnetic field. The extreme localization effect recently predicted for this periodic lattice is revealed as a suppression of the critical current when the applied magnetic field corresponds to half a flux quantum per unit cell. For this particular magnetic field, the observed vortex state configuration is highly disordered.Comment: 6 pages, 2 eps figures, submitted to Physica C. Title change

Interaction induced delocalisation for two particles in a periodic potential

We consider two interacting particles evolving in a one-dimensional periodic structure embedded in a magnetic field. We show that the strong localization induced by the magnetic field for particular values of the flux per unit cell is destroyed as soon as the particles interact. We study the spectral and the dynamical aspects of this transition.Comment: 4 pages, 5 EPS figures, minor misprints correcte

Coarsening on percolation clusters: out-of-equilibrium dynamics versus non linear response

We analyze the violations of linear fluctuation-dissipation theorem (FDT) in the coarsening dynamics of the antiferromagnetic Ising model on percolation clusters in two dimensions. The equilibrium magnetic response is shown to be non linear for magnetic fields of the order of the inverse square root of the number of sites. Two extreme regimes can be identified in the thermoremanent magnetization: (i) linear response and out-of-equilibrium relaxation for small waiting times (ii) non linear response and equilibrium relaxation for large waiting times. The function $X(C)$ characterizing the deviations from linear FDT cross-overs from unity at short times to a finite positive value for longer times, with the same qualitative behavior whatever the waiting time. We show that the coarsening dynamics on percolation clusters exhibits stronger long-term memory than usual euclidian coarsening.Comment: 17 pages, 10 figure

How to escape Aharonov-Bohm cages ?

We study the effect of disorder and interactions on a recently proposed magnetic field induced localization mechanism. We show that both partially destroy the extreme confinement of the excitations occuring in the pure case and give rise to unusual behavior. We also point out the role of the edge states that allows for a propagation of the electrons in these systems.Comment: 22 pages, 20 EPS figure

Vortex correlations in a fully frustrated two-dimensional superconducting network

7 pages, 6 figuresWe have investigated the vortex state in a superconducting dice network using the Bitter decoration technique at several magnetic frustrations f=1/2 and 1/3. In contrast to other regular network geometries where the existence of a commensurate state was previouly demonstrated, no ordered state was observed in the dice network at f=1/2 and the observed vortex-vortex correlation length is close to one lattice cell

Vortex correlations in a fully frustrated two-dimensional superconducting network

We have investigated the vortex state in a superconducting dice network using the Bitter decoration technique at several magnetic frustrations $f=\phi / \phi_{0}=1/2$ and 1/3. In contrast to other regular network geometries where the existence of a commensurate state was previouly demonstrated, no ordered state was observed in the dice network at f=1/2 and the observed vortex-vortex correlation length is close to one lattice cell

Polynesian traditional herbals in cosmetics and skin care: uses and potentials

International audienc

Polynesian cosmetopoeia: traditional uses and cosmetic potential

International audienc