Penetration of the magnetic field into a 3D ordered Josephson medium at very small values of the pinning parameter |
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Authors: | M A Zelikman |
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Institution: | 1.St. Petersburg State Polytechnical University,St. Petersburg,Russia |
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Abstract: | The Meissner state of a 3D Josephson medium is analyzed for stability against small fluctuations of phase discontinuities
at contacts. For any form of fluctuations, there exists value I
0 of pinning parameter I such that the Meissner configuration remains stable if I < I
0. Reasons why the configuration remains stable at small I are considered. Instability arises when the quadratic form of the second variation of Gibbs potential G is not a positively definite quantity. At small I, the contribution of the Josephson energy to G is small. The second variation of the magnetic energy, the other component of G, is always a positively definite quadratic form. Therefore, instability may arise only if I has a finite value. This statement holds true not only for the Meissner but also for any equilibrium configuration. At I < I
0, stability persists up to the boundary of the Meissner state. Then, a sequence of plane vortices parallel to the boundary
appears throughout the sample. Thus, vortices appearing at I < I
0 are plane vortices rather than linear. The configurations of currents and the magnetic field profile inside the sample are
calculated for I < I
0. Calculation is based on analyzing the continuous variation of the current configuration toward a decrease in the Gibbs potential. |
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Keywords: | |
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