Catastrophe observation in a Josephson junction system

TL;DR

This paper demonstrates that Thom's catastrophe theory accurately models the nonlinear behavior of SQUIDs, providing a quantitative match between theory and experimental observations of their complex dynamics.

Contribution

It offers the first direct quantitative comparison between catastrophe theory and experimental data on SQUIDs, confirming the theory's applicability to real superconducting systems.

Findings

Thom's catastrophe theory accurately describes SQUID behavior.

Experimental data matches the butterfly catastrophe model.

The model captures key nonlinear features of the system.

Abstract

We report on a direct quantitative comparison between Thom's general catastrophe theory for systems presenting discontinuous behavior and experimental reality. It is demonstrated that the model provides a striking quantitative description of the measured experimental features of the complex nonlinear system generating the most appealing class of sensors and devices nowadays used in experiments, namely the Superconducting Quantum Interference Devices (SQUIDs). The parameter space of the SQUID system that we investigate displays all the features associated with a butterfly catastrophe, namely a catastrophe expected for a system having four control parameters and one state variable.