Observation of negative absolute resistance in a Josephson junction

TL;DR

This paper reports the experimental observation of negative absolute resistance in a Josephson junction under microwave irradiation, with results aligning well with theoretical simulations based on a classical particle model.

Contribution

First experimental demonstration of negative absolute resistance in a Josephson junction under microwave current, supported by theoretical modeling and numerical simulations.

Findings

Negative resistance up to about -1Ω observed

NAR depends on microwave current amplitude

Experimental results agree with classical Brownian particle model

Abstract

We experimentally demonstrate the occurrence of negative absolute resistance (NAR) up to about $-1\Omega$ in response to an externally applied dc current for a shunted Nb-Al/AlO$_x$-Nb Josephson junction, exposed to a microwave current at frequencies in the GHz range. The realization (or not) of NAR depends crucially on the amplitude of the applied microwave current. Theoretically, the system is described by means of the resistively and capacitively shunted junction model in terms of a moderately damped, classical Brownian particle dynamics in a one-dimensional potential. We find excellent agreement of the experimental results with numerical simulations of the model.