Berezinskii-Kosterlitz-Thouless transition in Josephson junction arrays

Abstract

The quantum XY model shows a Berezinskii-Kosterlitz-Thouless (BKT) transition between a phase with quasi long-range order and a disordered one, like the corresponding classical model. The effect of the quantum fluctuations is to weaken the transition and eventually to destroy it. However, in this respect the mechanism of disappearance of the transition is not yet clear. In this work we address the problem of the quenching of the BKT in the quantum XY model in the region of small temperature and high quantum coupling. In particular, we study the phase diagram of a 2D Josephson junction array, that is one of the best experimental realizations of a quantum XY model. A genuine BKT transition is found up to a threshold value $g^{\star }$ of the quantum coupling, beyond which no phase coherence is established. Slightly below $g^{\star }$ the phase stiffness shows a reentrant behavior at lowest temperatures, driven by strong nonlinear quantum fluctuations. Such a reentrance is removed if the dissipation effect of shunt resistors is included.

14 pages, Kluwer style. Proceeding of the EURESCO conference "Fundamental Problems of Mesoscopic Physics", Sept. 2003, Granada

References in corpus (3)

• Superconductor-insulator quantum phase transition in a single Josephson junction
• Reentrant behavior of the phase stiffness in Josephson junction arrays
• Simulating Quantum Dissipation in Many-Body Systems

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