Intrinsic phase-locked state in two-dimensional Nb Josephson arrays

We present experimental results and numerical simulations of a new phase-locked state in two-dimensional arrays when nearly fully frustrated and driven by a dc current. In this state, all the rows of the array act coherently and phase-lock at a voltage that depends on the geometric loop inductance and junction capacitance. We also experimentally observe the resonance in one-dimensional ladder arrays, implying that two-dimensional arrays have inter-row phase-locking mechanisms. The horizontal junctions also appear to play a role in the dynamics. Two-dimensional arrays have been proposed as tunable microwave oscillators.