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arXiv · 0808.2678

Y-junction of superconducting Josephson chains

Domenico Giuliano·Pasquale Sodano
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Abstract

We show that, for pertinent values of the fabrication and control parameters, an attractive finite coupling fixed point emerges in the phase diagram of a Y-junction of superconducting Josephson chains. The new fixed point arises only when the dimensionless flux $f$ piercing the central loop of the network equals $π$ and, thus, does not break time-reversal invariance; for $f \neq π$, only the strongly coupled fixed point survives as a stable attractive fixed point. Phase slips (instantons) have a crucial role in establishing this transition: we show indeed that, at $f = π$, a new set of instantons -the W-instantons- comes into play to destabilize the strongly coupled fixed point. Finally, we provide a detailed account of the Josephson current-phase relationship along the arms of the network, near each one of the allowed fixed points. Our results evidence remarkable similarities between the phase diagram accessible to a Y-junction of superconducting Josephson chains and the one found in the analysis of quantum Brownian motion on frustrated planar lattices.

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Domenico Giuliano, Pasquale Sodano. 2009-01-21. Y-junction of superconducting Josephson chains. https://doi.org/10.1016/j.nuclphysb.2008.11.011

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