Dynamical phase transition in a fully frustrated Josephson array on a square lattice

Abstract

We study dynamical phase transitions at temperature T=0 in a fully frustrated square Josephson junction array subject to a driving current density, which has nonzero components ix, iy parallel to both axes of the lattice. Our numerical results show clear evidence for three dynamical phases: a pinned vortex lattice characterized by zero time-averaged voltages 〈vx〉t and 〈vy〉t, a “plastic” phase in which both 〈vx〉t and 〈vy〉t are nonzero, and a moving lattice phase in which only one of the time-average voltage components is nonzero. The last of these has a finite transverse critical current: if a current is applied in the x direction, a nonzero transverse current density iy is required before 〈vy〉t becomes nonzero. The voltage traces in the moving lattice phase are periodic in time. By contrast, the voltages in the plastic phase have continuous power spectra that are weakly dependent on frequency. This phase diagram is found numerically to be qualitatively unchanged by the presence of weak disorder. We also describe two simple analytical models that recover some, but not all, the characteristics of the three dynamical phases, and of the phase diagram calculated numerically.

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