Dissipation mechanism above the current threshold in Josephson junction chains

TL;DR

This paper investigates the dissipation mechanisms in Josephson junction chains near the current threshold, revealing flux-dependent conductance and viscous Cooper pair dynamics through experimental measurements and $P(E)$ theory.

Contribution

It provides the first detailed experimental analysis of dissipation above the current threshold in Josephson junction chains with flux-dependent conductance.

Findings

Observation of a blockaded zero current branch at low bias

Discontinuous transition to a dissipative, flux-dependent conductance above $V_{sw}$

Periodic flux dependence of conductance consistent with $P(E)$ theory

Abstract

We present measurements on one-dimensional Josephson junction arrays formed by a chain of SQUID loops in the regime where $E_J / E_c\simeq 1$. We observe a blockaded zero current branch for small bias voltages. Above a certain voltage $V_\mathrm{sw}$ the $I$-$V$ characteristics changes discontinuously to a dissipative branch characterized by a flux dependent conductance. Three of four samples show a pronounced hysteresis for a forward and backward voltage sweep. We observe a periodic field dependence of the conductance above $V_\mathrm{sw}$ which can be described with $P(E)$ theory for cooper-pairs and therefore gives evidence of viscous dynamics of Cooper pair transport through the array.