Achieving the threshold regime with an over-screened Josephson junction

TL;DR

This paper shows how an over-screened Josephson junction can be used as a noise detector to measure rare current fluctuations, revealing a non-Arrhenius activation behavior in the threshold regime.

Contribution

It introduces a novel method using over-screened Josephson junctions to access the threshold regime and measure fluctuation tails in mesoscopic conductors.

Findings

Over-screened Josephson junctions enable threshold regime measurement.

Activation rate deviates from Arrhenius law in this setup.

External circuit impedance controls the activation barrier.

Abstract

We demonstrate that by utilizing an over-screened Josephson junction as a noise detector it is possible to achieve the threshold regime, whereby the tails of the fluctuating current distribution are measured. This situation is realized by placing the Josephson junction and mesoscopic conductor in an external circuit with very low impedance. In the underdamped limit, over-screening the junction inhibits the energy diffusion in the junction, effectively creating a tunable activation barrier to the dissipative state. As a result, the activation rate is qualitatively different from the Arrhenius form.