Wohlleben effect in small grains of Bi-based high-temperature superconductors: evidence for intrinsic nature of spontaneous currents

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1996 EDP Sciences
, , Citation N. Knauf et al 1996 EPL 35 541 DOI 10.1209/epl/i1996-00148-y

0295-5075/35/7/541

Abstract

We report on the observation of the Wohlleben effect (WE) in powders of Bi-based high-temperature superconductors consisting of isolated grains with sizes of order 1 μm. In these small grains the Josephson contacts with negative critical current (π-junctions) generally involved to explain the WE must be able to carry a current density of order j ≈ 105 − 106 A/cm2, even close to Tc. Such high spontaneous currents can be explained, if such contacts are not ordinary tunneling Josephson junctions but superconductor–normal-metal–superconductor junctions and if the superconducting order parameter has d-wave symmetry.

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10.1209/epl/i1996-00148-y