Josephson oscillation linewidth of ion-irradiated YBa$_2$Cu$_3$O$_7$ junctions

TL;DR

This study investigates the noise characteristics and linewidth of ion-irradiated YBa2Cu3O7 Josephson junctions at approximately 132 GHz, highlighting the dominant Johnson noise and potential for frequency-tunable oscillators.

Contribution

It provides the first detailed analysis of noise sources affecting the linewidth of ion-irradiated high-Tc Josephson junctions and compares experimental results with a theoretical model.

Findings

Johnson noise is the main low-frequency fluctuation source.

Excess 1/f noise is not dominant in the studied temperature range.

Ion-irradiated junctions are promising for frequency-tunable oscillator applications.

Abstract

We report on the noise properties of ion-irradiated YBa$_2$Cu$_3$O$_7$ Josephson junctions. This work aims at investigating the linewidth of the Josephson oscillation with a detector response experiment at $\simeq$132 GHz. Experimental results are compared with a simple analytical model based on the Likharev-Semenov equation and the de Gennes dirty limit approximation. We show that the main source of low-frequency fluctuations in these junctions is the broadband Johnson noise and that the excess ($\frac{1}{f}$) noise contribution does not prevail in the temperature range of interest, as reported in some other types of high-T$_c$ superconducting Josephson junctions. Finally, we discuss the interest of ion-irradiated junctions to implement frequency-tunable oscillators consisting of synchronized arrays of Josephson junctions.