Reentrant phase transition in granular superconductors

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Abstract

The conditions for the appearance of a reentrant superconducting phase in granular materials are studied in mean field approximation applied to periodic models. We assume that the relevant low-lying excitation is the transfer of a Cooper pair from a grain to one of its neighbours, and neglect pair breaking. Both on-grain (U) and nearest neighbour (V) Coulomb interactions are taken into account, and the Coulomb problem is treated in Bethe-Peierls approximation. When V/U is not too large, reentrance is predicted if V/U>(4+3 z)-1/2 where z is the coordination number. This result is different from a recent criterion suggested by Šimánek, which allows reentrance only in the immediate vicinities of certain discrete values of V/U. For strong enough V/U, the models treated here show a transition to an ionic-salt-like charge-ordered state. Reentrant superconductivity is shown to occur also on an ionic background. In actual systems, close-packing effects partially frustrate the ionic ordering and enhance the reentrant feature.

Original languageEnglish
Pages (from-to)215-221
Number of pages7
JournalZeitschrift füur Physik B Condensed Matter
Volume45
Issue number3
DOIs
Publication statusPublished - Sep 1982

ASJC Scopus subject areas

  • Condensed Matter Physics

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