Abstract

The Josephson effect, tunnelling of a supercurrent through a thin insulator layer between two superconducting islands, is a phenomena characterized by a spatially distributed phase of the superconducting condensate. In recent years, there has been a growing focus on Josephson junction devices particularly for the applications of quantum metrology and superconducting qubits. In this study, we report the development of Josephson junction circuit formed by serially connecting many Superconducting Quantum Interference Devices, SQUIDs. We present experimental measurements as well as numerical simulations of a phase-slip center, a SQUID with weaker junctions, embedded in a Josephson junction chain. The DC transport properties of the chain are the result of phase slips which we simulate using a classical model that includes linear external damping, terminating impedance, as well as internal nonlinear quasiparticle damping. We find good agreement between the simulated and the experimental current voltage characteristics. The simulations allow us to examine the spatial and temporal distribution of phase-slip events occurring across the chains and also the existence of travelling voltage pulses which reflect at the chain edges.

Highlights

  • Josephson junction chains (JJCs) are a model system for understanding superconductivity in one dimension[1]

  • The low-temperature dynamics of this phase depends on three characteristic parameters of the individual junctions: The Josephson Coupling energy EJ = ICħ/2e, where IC is the junction critical current; the single electron charging energy EC = e2/2C, where C is the junction capacitance; and the damping in the electromagnetic environment seen by the junction, represented by a series resistance Rdamp

  • And above the gap voltage, regions of negative differential conductance are observed. In this low-field regime we show the differential conductance at minimum EJ of the phase-slip center (PSC) (Fig. 2d)

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Summary

Introduction

Josephson junction chains (JJCs) are a model system for understanding superconductivity in one dimension[1] They find important technological application in quantum metrology for realization of the SI unit Volt[2] and as a microwave amplifier for quantum-limited signal amplification[3, 4]. When RQ/Rdamp 1, quantum phase-slips are rare and the JJC can be described as a Josephson element with a modified current-phase relation[22]. The role of the damping resistance Rdamp is interesting in long JJC’s because the linear dynamics of the chain is that of a high impedance transmission line for distributed Josephson plasmon modes[23]. EC0 = e2/2C0 is the charging energy associated with the capacitance of each island to ground C0 This radiation damping impedance plays the role of Rdamp. 1 (corresponding to α 1) and EC >∼ EJ, coherent windings of the phase, give rise to a classical description

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