Observation of Bifurcations and Hysteresis in Nonlinear NbN Superconducting Microwave Resonators

TL;DR

This paper reports the observation of complex nonlinear behaviors such as bifurcations, hysteresis, and frequency drift in NbN superconducting microwave resonators, revealing new insights into their dynamic responses.

Contribution

It introduces the observation of multiple nonlinear phenomena in NbN resonators and hypothesizes weak links as their source, advancing understanding of superconducting microwave device behavior.

Findings

Observation of bifurcations and hysteresis in resonance curves

Detection of multiple jumps and frequency drift

Identification of weak links as nonlinear sources

Abstract

In this paper we report some extraordinary nonlinear dynamics measured in the resonance curve of NbN superconducting stripline microwave resonators. Among the nonlinearities observed: aburpt bifurcations in the resonance response at relatively low input powers, asymmetric resonances, multiple jumps within the resonance band, resonance frequency drift, frequency hysteresis, hysteresis loops changing direction and critical coupling phenomenon. Weak links in the NbN grain structure are hypothesized as the source of the nonlinearities.