Resolving the effects of frequency dependent damping and quantum phase diffusion in YBa$_2$Cu$_3$O$_{7-x}$ Josephson junctions

TL;DR

This study investigates the phase dynamics of high-temperature superconductor Josephson junctions, revealing how frequency-dependent damping and quantum phase diffusion influence their behavior, with implications for quantum device design.

Contribution

It introduces a detailed analysis of YBCO grain boundary Josephson junctions, highlighting the role of frequency-dependent damping and quantum phase diffusion in their dynamics.

Findings

Frequency-dependent damping modeled with two quality factors.

Observation of quantum phase diffusion regime.

Correlation between device parameters and phase transition signatures.

Abstract

We report on the study of the phase dynamics of high critical temperature superconductor Josephson junctions. We realized YBa$_2$Cu$_3$O$_{7-x}$ (YBCO) grain boundary (GB) biepitaxial junctions in the submicron scale, using low loss substrates, and analyzed their dissipation by comparing the transport measurements with Monte Carlo simulations. The behavior of the junctions can be fitted using a model based on two quality factors, which results in a frequency dependent damping. Moreover, our devices can be designed to have Josephson energy of the order of the Coulomb energy. In this unusual energy range, phase delocalization strongly influences the device's dynamics, promoting the transition to a quantum phase diffusion regime. We study the signatures of such a transition by combining the outcomes of Monte Carlo simulations with the analysis of the device's parameters, the critical current and the temperature behavior of the low voltage resistance $R_0$.