Imaging of Microscopic Sources of Resistive and Reactive Nonlinearities in Superconducting Microwave Devices

TL;DR

This paper uses advanced low-temperature Laser Scanning Microscopy to spatially resolve and analyze the microscopic sources of nonlinear microwave responses in superconducting thin-film resonators, revealing resistive domains as primary contributors.

Contribution

The study introduces a faster, modified impedance partitioning method for LSM, enabling detailed 2D mapping of nonlinear sources in superconducting microwave devices.

Findings

Resistive domains are the main sources of nonlinear microwave response.

The modified LSM procedure significantly speeds up the analysis.

Micron-scale spatial variations of intermodulation currents are successfully mapped.

Abstract

The technique of low-temperature Laser Scanning Microscopy (LSM) has been applied to the investigation of local microwave properties in operating YBa2Cu3O7/LaAlO3 thin-film resonators patterned into a meandering strip transmission line. By using a modified newly developed procedure of spatially-resolved complex impedance partition, the influence of inhomogeneous current flow on the formation of nonlinear (NL) microwave response in such planar devices is analyzed in terms of the independent impact from resistive and inductive components. The modified procedure developed here is dramatically faster than our previous method. The LSM capability to probe the spatial variations of two-tone, third-order intermodulation currents on micron length scales is used to find the 2D distribution of the local sources of microwave NL. The results show that the dominant sources of microwave NL are strongly localized in the resistive domains.