Ground states of one and two fractional vortices in long Josephson 0−κ junctions

E. Goldobin; D. Koelle; R. Kleiner

doi:10.1103/PhysRevB.70.174519

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Ground states of one and two fractional vortices in long Josephson 0−κ junctions

E. Goldobin, D. Koelle, R. Kleiner

DOI 10.1103/PhysRevB.70.174519 · Physical Review B

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Abstract

Half-integer Josephson vortices in 0−π junctions, discussed theoretically and observed experimentally, spontaneously appear at the point where the Josephson phase is π discontinuous. The creation of arbitrary discontinuities of the Josephson phase has been demonstrated recently. Here we study fractional vortices formed at an arbitrary κ discontinuity and discuss their stability and possible ground states. The two stable states are not mirror symmetric. Furthermore, the possible ground states formed at two κ discontinuities separated by a distance a are investigated, and the energy and regions of stability of each ground state are calculated. We also show that the ground states may strongly depend on the distance a between the discontinuities. There is a crossover distance ac such that for a<ac and for a>ac the ground states may be qualitatively different.