Long Josephson Junction in a Resonant Cavity

TL;DR

This paper models a long Josephson junction coupled to a resonant cavity, revealing how cavity coupling influences voltage steps and soliton dynamics, with implications for understanding quantum magnetic flux phenomena.

Contribution

It introduces a detailed model of a long Josephson junction interacting with a single-mode cavity, analyzing effects of electric and magnetic coupling on junction behavior and soliton dynamics.

Findings

Self-induced resonant steps observed in voltage due to cavity coupling.

Strong coupling causes soliton phase-locking and anomalies in IV characteristics.

Cavity mode frequency shifts significantly under strong coupling.

Abstract

We present a model to describe an underdamped long Josephson junction coupled to a singlemode electromagnetic cavity, and carry out numerical calculations using this model in various regimes. The coupling may occur through either the electric or the magnetic eld of the cavity mode. When a current is injected into the junction, we nd that the time-averaged voltage exhibits self-induced resonant steps due to coupling between the current in the junction and the electric eld of the cavity mode. These steps are similar to those observed and calculated in small Josephson junctions. When a soliton is present in the junction (corresponding to a quantum of magnetic ux parallel to the junction plates), the SIRS's disappear if the electric eld in the cavity is spatially uniform. If the cavity mode has a spatially varying electric eld, there is a strong coupling between the soliton and the cavity mode. This coupling causes the soliton to become phase-locked to the cavity mode, and produces step-like anomalies on the soliton branch of the IV characteristics. If the coupling is strong enough, the frequency of the cavity mode is greatly red-shifted from its uncoupled value. We present simple geometrical arguments which account for this behavior.