Tunable ±φ,φ0, and φ0±φ Josephson junction

E. Goldobin; D. Koelle; R. Kleiner

doi:10.1103/PhysRevB.91.214511

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Tunable ±φ,φ0, and φ0±φ Josephson junction

E. Goldobin, D. Koelle, R. Kleiner

DOI 10.1103/PhysRevB.91.214511 · Physical Review B

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Abstract

We study a 0-π dc superconducting quantum interference device (SQUID) with asymmetric inductances and critical currents of the two Josephson junctions (JJs). By considering such a dc SQUID as a black box with two terminals, we calculate its effective current-phase relation Is(ψ) and the Josephson energy U(ψ), where ψ is the Josephson phase across the terminals. We show that there is a domain of parameters where the black box has the properties of a φ JJ with degenerate ground state phases ψ=±φ. The φ domain is rather large, so one can easily construct a φ JJ experimentally. We derive the current phase relation and show that it can be tuned in situ by applying an external magnetic flux resulting in a continuous transition between the systems with static solutions ψ=±φ,ψ=φ0 (φ0≠0,π) and even ψ=φ0±φ. The dependence of φ0 on applied magnetic flux is not 2π (one flux quantum) periodic.