I-Vcharacteristics in two-dimensional frustrated Josephson-junction arrays

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Abstract
Langevin molecular-dynamics simulations of two-dimensional Josephson-junction arrays in a uniform external magnetic field are presented. I-V characteristics for zero and finite temperature are calculated. The voltage response is analyzed in terms of the dynamical behavior of defects with respect to the ground-state flux lattice—domain walls and vortex-antivortex pairs. At zero temperature, several spatio-temporal regimes as a function of I are found: (i) a superconducting phase (V=0) corresponding to the locking of the flux lattice; (ii) a ‘‘chaotic’’ response related to domain walls nearly pinned by the discreteness of the underlying flux lattice; and (iii) two phases with ac response corresponding to different periodic domain-wall lattice patterns. At finite temperatures the response is modified by the nucleation of transverse structure (vortex-antivortex pairs) on the moving domain walls. This instability can enhance or inhibit the voltage response depending on the domain-wall structure. A phase diagram of the different dynamical regimes is proposed.