Anomalous thermal escape in Josephson systems perturbed by microwaves

TL;DR

This study explores how microwave radiation influences thermal activation and switching behaviors in Josephson junctions, revealing multi-valued switching currents and resonance effects near the quantum crossover temperature through experiments and simulations.

Contribution

It demonstrates the resonance-induced multi-valued switching currents and validates an anharmonic theory for Josephson plasma frequency with experimental and numerical data.

Findings

Resonance with plasma frequency causes multi-valued switching currents.

Good agreement between experiments, simulations, and anharmonic theory.

Switching current distributions vary with temperature and microwave frequency.

Abstract

We investigate, by experiments and numerical simulations, thermal activation processes of Josephson tunnel junctions in the presence of microwave radiation. When the applied signal resonates with the Josephson plasma frequency oscillations, the switching current may become multi-valued temperature ranges both below and above the the classical to quantum crossover temperature. Switching current distributions are obtained both experimentally and numerically at temperatures both near and far above the quantum crossover temperature. Plots of the switching currents traced as a function of the applied signal frequency show very good agreement with a simple anharmonic theory for Josephson resonance frequency as a function of bias current. Throughout, experimental results and direct numerical simulations of the corresponding thermally driven classical Josephson junction model show very good agreement.