Pairing of Cooper pairs in a Josephson junction network containing an impurity

Abstract

We show how to induce pairing of Cooper pairs (and, thus, $4e$ superconductivity) as a result of local embedding of a quantum impurity in a Josephson network fabricable with conventional junctions. We find that a boundary double Sine-Gordon model provides an accurate description of the dc Josephson current patterns, as well as of the stable phases accessible to the network. We point out that tunneling of pairs of Cooper pairs is robust against quantum fluctuations, as a consequence of the time reversal invariance, arising when the central region of the network is pierced by a dimensionless magnetic flux $\varphi =\pi$. We find that, for $\varphi =\pi$, a stable attractive finite coupling fixed point emerges and point out its relevance for engineering a two level quantum system with enhanced coherence.

5 Pages, 5 Figures. Small modifications, ref.[11] added. To appear in EPL

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• Competing orders in one dimensional spin 3/2 fermionic systems
• Two-electron bunching in transport through a QD induced by Kondo correlations
• Y-junction of superconducting Josephson chains
• Frustration of Decoherence in Open Quantum Systems
• Frustration of decoherence in $Y$-shaped superconducting Josephson networks
• Quantum Impurity Problems in Condensed Matter Physics
• Pairing of Cooper pairs in a Josephson junction network containing an impurity
• Boundary Field Theory Approach to the Renormalization of SQUID Devices

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• XXZ spin-1/2 representation of a finite-U Bose-Hubbard chain at half-integer filling
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