Time-domain response of displaced linear branch in long Josephson junction
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At low fluxon density, the flux-flow state in a long Josephson tunnel junction is manifested by the so called displaced linear slope (DLS) appearing as a smooth resonance-free branch in current-voltage characteristics. For the DLS branch, we measured the Josephson radiation linewidth by factor of 104 larger than that of a equivalent lumped Josephson oscillator. With increasing the fluxon density, a sharp crossover is observed to a much smaller linewidth approaching the lumped oscillator limit. Numerical simulations using perturbed sine-Gordon model indicate that the observed behavior is related to the internal degrees of freedom in the weakly interacting fluxon chain which dynamics becomes intrinsically chaotic.
KeywordsJosephson Junction Chaotic State Magnetic Field Range Fourier Power Spectrum Junction Boundary