Microscopic Model of Critical Current Noise in Josephson Junctions

TL;DR

This paper introduces a microscopic model explaining how two-level systems in Josephson junction barriers cause critical current noise, matching experimental data and highlighting the impact of barrier nonuniformity.

Contribution

The paper presents a simple microscopic model linking two-level systems to critical current noise, with predictions matching experimental observations.

Findings

Critical current noise exhibits a 1/f spectrum proportional to L^5.

Model predictions align well with recent experimental measurements.

Barrier nonuniformity significantly affects noise sensitivity.

Abstract

We present a simple microscopic model to show how fluctuating two--level systems in the Josephson junction tunnel barrier of thickness $L$ can modify the potential energy of the barrier and produce critical current noise spectra. We find low frequency $1/f$ noise that goes as $L^5$. Our values are in good agreement with recent experimental measurements of critical current noise in Al/AlO$_{x}$/Al Josephson junctions. We also investigate the sensitivity of the noise on the nonuniformity of the tunnel barrier.