Frequency pulling and mixing of relaxation oscillations in superconducting nanowires

TL;DR

This paper demonstrates that superconducting nanowires can exhibit Josephson-like relaxation oscillations modulated by microwaves, opening new avenues for applications in amplification and multiplexing.

Contribution

It shows that resistively shunted superconducting nanowires can produce high-frequency relaxation oscillations similar to Josephson junctions, with controllable frequency pulling and mixing.

Findings

Nanowire oscillations can be phase-locked by microwave signals.

Hotspot dynamics in nanowires mimic Josephson junction behavior.

Potential for nanowire-based parametric amplification and multiplexing.

Abstract

Many superconducting technologies such as rapid single flux quantum computing (RSFQ) and superconducting quantum interference devices (SQUIDs) rely on the modulation of nonlinear dynamics in Josephson junctions for functionality. More recently, however, superconducting devices have been developed based on the switching and thermal heating of nanowires for use in fields such as single photon detection and digital logic. In this paper, we use resistive shunting to control the nonlinear heating of a superconducting nanowire and compare the resulting dynamics to those observed in Josephson junctions. We show that interaction of the hotspot growth with the external shunt produces high frequency relaxation oscillations with similar behavior as observed in Josephson junctions due to their rapid time constants and ability to be modulated by a weak periodic signal. In particular, we use a microwave drive to pull and mix the oscillation frequency, resulting in phase locked features that resemble the AC Josephson effect. New nanowire devices based on these conclusions have promising applications in fields such as parametric amplification and frequency multiplexing.