Percolation model for the superconductor-insulator transition in granular films

The effect of disorder is investigated in granular superconductive materials with strong and weak links. The transition is controlled by the interplay of the tunneling g and intragrain g intr conductances, which depend on the strength of the intergrain coupling. For g ≪ g intr , the transition involves first the grain boundary, while for g ∼ g intr the transition occurs into the whole grain. The different intergrain coupling is considered by modelling the superconducting material as a disordered network of Josephson junctions. Numerical simulations show that on increasing the disorder, the resistive transition occurs for lower temperatures and the curve broadens. These features are enhanced in disordered superconductors with strong links. The different behaviour is further checked by estimating the average network resistance for weak and strong links in the framework of the effective medium approximation theory. These results may be relevant to shed light on long standing puzzles as: (i) enhancement of the superconducting transition temperature of many metals in the granular states; (ii) suppression of superconductivity in homogeneously disordered films compared to standard granular systems close to the metal-insulator transition; (iii) enhanced degradation of superconductivity by doping and impurities in strongly linked materials, such as magnesium diboride, compared to weakly-linked superconductors, such as cuprates.

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“…7. To explain this issue, the elementary resistance between two neighboring sites i and j will be now estimated by using [65,66,67,68]:…”

Section: Discussionmentioning

confidence: 99%

Resistive transition in disordered superconductors with varying intergrain coupling

Ponta

Carbone

Gilli

2010

Supercond. Sci. Technol.

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“…But the nature of the transition at T co is still unclear. Percolation model can be applied in granular superconductors to give a microscopic explanation of the coherent transition [15,16]. One can assume that the free energy of system is divided into two parts, that is, one is associated with the isolated grains and the other is related to the interactions among the grains.…”

Section: Discussionmentioning

confidence: 99%

Granular superconductivity in polycrystalline Bi2Sr2CaCu2O8+δ by homovalent La substitution on Bi sites

Zhang

et al. 2010

Journal of Non-Crystalline Solids

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“…The Effective Medium Approximation 33,51,52,56,[64][65][66][67][68] (as well as Clausius-Mossotti approximation) used above takes into account the shapes of the islands (through their depolarization factor n) and their sizes (through their volume fraction p 1 ) but does not take into account the distances between the islands. In order to take into account the latter we propose to make a coordinate transformation x =ĝ(x) · x, which transforms space in such a way that the distances between the inclusions become the same (see top of Fig.…”

Section: Laminate Approximation For Periodic Array Of Closely Packed mentioning

confidence: 99%

Manipulating the optical transparency of anisotropic metamaterials with magnetic field and liquid crystals: influence of the nanostructures shape

et al. 2009

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The light transmission through metallic films with different types of nano-structures was studied both theoretically and experimentally. It is shown, analytically, numerically and experimentally, that the positions of the surface plasmon resonances depend on nano-structural details. This leads to a strong dependence of the amplitude of the light transmission, as well as the polarization of the transmitted light and other optical properties, on those details. Two complementary situations are considered: a metal film with dielectric holes and a dielectric film with metallic islands. Two different possibilities for manipulating the light transmission are considered: One is based upon application of a static magnetic field (actually, this is equivalent to changing the nano-structure in a transformed configuration space), the other is based upon using liquid crystals as one of the constituents of a nano-structured film.

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Percolation model for the superconductor-insulator transition in granular films

Cited by 42 publications

References 78 publications

Resistive transition in disordered superconductors with varying intergrain coupling

Resistive transition in disordered superconductors with varying intergrain coupling

Granular superconductivity in polycrystalline Bi2Sr2CaCu2O8+δ by homovalent La substitution on Bi sites

Manipulating the optical transparency of anisotropic metamaterials with magnetic field and liquid crystals: influence of the nanostructures shape

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