Josephson Junction with a Magnetic-Field Tunable Ground State

E. Goldobin; D. Koelle; R. Kleiner; R. G. Mints

doi:10.1103/PhysRevLett.107.227001

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Josephson Junction with a Magnetic-Field Tunable Ground State

E. Goldobin, D. Koelle, R. Kleiner, R. G. Mints

DOI 10.1103/PhysRevLett.107.227001 · Physical Review Letters

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Abstract

We consider an asymmetric 0−π Josephson junction consisting of 0 and π regions of different lengths L0 and Lπ. As predicted earlier this system can be described by an effective sine-Gordon equation for the spatially averaged phase ψ so that the effective current-phase relation of this system includes a negative second harmonic ∝sin(2ψ). If its amplitude is large enough, the ground state of the junction is doubly degenerate ψ=±φ, where φ depends on the amplitudes of the first and second harmonics. We study the behavior of such a junction in an applied magnetic field H and demonstrate that H induces an additional term ∝Hcosψ in the effective current-phase relation. This results in a nontrivial ground state tunable by magnetic field. The dependence of the critical current on H allows for revealing the ground state experimentally.