Pinning of charge and flux solitons in disordered Josephson junction arrays

Kirill G. Fedorov; Mikhail V. Fistul; Alexey V. Ustinov

doi:10.1103/PhysRevB.84.014526

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Pinning of charge and flux solitons in disordered Josephson junction arrays

Kirill G. Fedorov, Mikhail V. Fistul, Alexey V. Ustinov

DOI 10.1103/PhysRevB.84.014526 · Physical Review B

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Abstract

We study the depinning of flux and charge solitons in discrete Josephson junction arrays with magnetic and charge inhomogeneities, respectively. The dependencies of soliton depinning force on the discreteness parameter a of the system and on the magnitude of disorder are calculated numerically and analytically. We obtain that for small values of discreteness (a<1), magnetic (charge) inhomogeneities lead to a substantial increase of soliton depinning force with increasing the soliton size. In the opposite limit of a≳1, the Peierls-Nabarro potential induced by discreteness of array, results in a strong decrease of the depinning force with the size of soliton. Thus, the dependence of pinning force on 1/a displays a pronounced minimum, and its position is determined by a strength of disorder. We find the optimal charge soliton size, which is favorable for overcoming pinning induced by disorder. In case of small but finite disorder, increase in the soliton size finally leads to a destruction of the soliton by strong spatial fluctuations.