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arXiv · 1110.2326

Josephson junction with magnetic-field tunable ground state

E. Goldobin·D. Koelle·R. Kleiner·R. G. Mints
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Abstract

We consider an asymmetric 0-pi Josephson junction consisting of 0 and pi regions of different lengths L_0 and L_pi. As predicted earlier this system can be described by an effective sine-Gordon equation for the spatially averaged phase psi so that the effective current-phase relation of this system includes a \emph{negative} second harmonic ~sin(2 psi). If its amplitude is large enough, the ground state of the junction is doubly degenerate psi=\pmvarphi, where varphi 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 ~H cos(psi) in the effective current-phase relation. This results in a non-trivial ground state \emph{tunable} by magnetic field. The dependence of the critical current on H allows for revealing the ground state experimentally.

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E. Goldobin, D. Koelle, R. Kleiner, R. G. Mints. 2011-10-11. Josephson junction with magnetic-field tunable ground state. https://doi.org/10.1103/physrevlett.107.227001

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