Quantum phase slips in Josephson junction rings

Year: 2013

Authors: Rastelli G., Pop I. M., Hekking F. W.J.

Autors Affiliation: Universite Grenoble Alpes; Universitdt Konstanz; CNRS Centre National de la Recherche Scientifique; Yale University

Abstract: We study quantum phase-slip (QPS) processes in a superconducting ring containing N Josephson junctions and threaded by an external static magnetic flux ?. In such a system, a QPS consists of a quantum tunneling event connecting two distinct classical states of the phases with different persistent currents. When the Josephson coupling energy E of the junctions is larger than the charging energy E=e2/2C, where C is the junction capacitance, the quantum amplitude for the QPS process is exponentially small in the ratio E/E. At given magnetic flux, each QPS can be described as the tunneling of the phase difference of a single junction of almost 2?, accompanied by a small harmonic displacement of the phase difference of the other N-1 junctions. As a consequence, the total QPS amplitude ? is a global property of the ring. Here, we study the dependence of ? on the ring size N, taking into account the effect of a finite capacitance C to ground, which leads to the appearance of low-frequency dispersive modes. Josephson and charging effects compete and lead to a nonmonotonic dependence of the ring?s critical current on N. For N->?, the system converges either towards a superconducting or an insulating state, depending on the ratio between the charging energy E=e2/2C and the Josephson coupling energy E. (c) 2013 American Physical Society.

Journal/Review: PHYSICAL REVIEW B

Volume: 87 (17)      Pages from:   to:

More Information: We thank W. Guichard, L. Glazman, M. Vanevic, L. Amico, and L. Ioffe for useful discussions. This work was supported by ANR through contracts DYCOSMA and QUANTJO. We acknowledge support from the European networks MIDAS, SOLID, and GEOMDISS and from Institut universitaire de France.
KeyWords: quantum phase slips, josephson junction chains
DOI: 10.1103/PhysRevB.87.174513

ImpactFactor: 3.664
Citations: 58
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