Coherent Activation of Zero-Field Fiske Modes in Arrays of Josephson Junctions

TL;DR

This paper demonstrates that arrays of Josephson junctions can exhibit a coherent mode where all junctions oscillate synchronously at zero magnetic field, with resonance amplitudes increasing linearly with summed voltages.

Contribution

It reveals the existence of a zero-field coherent Fiske mode in Josephson junction arrays and characterizes its magnetic field response and boundary flux dynamics.

Findings

Resonance current amplitude increases linearly with summed voltages.

Coherent oscillations occur without external magnetic field.

Boundary flux dynamics are involved in the mode activation.

Abstract

Series arrays of Josephson junctions show evidence of a mode in which all the junctions oscillate in synchronism on voltage resonances appearing, in zero external magnetic field, at multiples of the fundamental Fiske step spacing. The measurements show that the current amplitude of the resonances increases linearly as their voltages are summed. Investigation of the nature of the coherent mode by magnetic field responses of arrays and isolated juctions reveals that the oscillations take place in a parameter plane region where dc magnetic fields only activate boundary current and flux-quanta dynamics can take place.