Fiske Steps and Abrikosov Vortices in Josephson Tunnel Junctions

TL;DR

This paper investigates how Abrikosov vortices influence Fiske resonances in small Josephson junctions, revealing that vortices induce Fiske steps without external magnetic fields and affect their magnitude and position.

Contribution

The study provides a combined theoretical and experimental analysis of vortex effects on Fiske steps, including the first measurement of vortex-induced changes in small Nb Josephson junctions.

Findings

Fiske steps can occur without external magnetic fields due to Abrikosov vortices.

Vortex density and misalignment affect Fiske step magnitudes.

Critical current decreases with increasing vortex density.

Abstract

We present a theoretical and experimental study of the Fiske resonances in the current-voltage characteristics of "small" Josephson junctions with randomly distributed misaligned Abrikosov vortices. We obtained that in the presence of Abrikosov vortices the resonant interaction of electromagnetic waves, excited inside a junction, with the ac Josephson current manifests itself by Fiske steps in a current-voltage characteristics even in the absence of external magnetic field. We found that the voltage positions of the Fiske steps are determined by a junction size, but the Fiske step magnitudes depend both on the density of trapped Abrikosov vortices and on their misalignment parameter. We measured the magnetic field dependence of both the amplitude of the first Fiske step and the Josephson critical current of low-dissipative small $Nb$ based Josephson tunnel junctions with artificially introduced Abrikosov vortices. A strong decay of the Josephson critical current and a weak non-monotonic decrease of the first Fiske step amplitude on the Abrikosov vortex density were observed. The experimentally observed dependencies are well described by the developed theory.