Cryogenic Digital Image Correlation as a Probe of Strain in Iron-Based Superconductors

TL;DR

This paper demonstrates the use of cryogenic digital image correlation as a high-resolution, non-contact method to measure surface strains in iron-based superconductors, aiding the study of strain effects on their electronic properties.

Contribution

It introduces a cryogenic optical system with digital image correlation for precise, full-field strain measurement in superconductors, offering an accessible alternative to traditional methods.

Findings

Digital image correlation provides high spatial resolution strain measurements.

Results are consistent with X-ray and neutron diffraction measurements.

The method facilitates studying strain effects in quantum materials.

Abstract

Uniaxial strain is a powerful tuning parameter that can control symmetry and anisotropic electronic properties in iron-based superconductors. However, accurately characterizing anisotropic strain can be challenging and complex. Here, we utilize a cryogenic optical system equipped with a high-spatial-resolution microscope to characterize surface strains in iron-based superconductors using the digital image correlation method. Compared with other methods such as high-resolution X-ray diffraction, strain gauge, and capacitive sensor, digital image correlation offers a non-contact, full-field measurement approach, acting as an optical virtual strain gauge that provides high spatial resolution. The results measured on detwinned {\BFA} are quantitatively consistent with the distortion measured by X-ray diffraction and neutron Larmor diffraction. These findings highlight the potential of cryogenic digital image correlation as an effective and accessible tool for probing the isotropic and anisotropic strains, facilitating the application of uniaxial strain tuning in the study of quantum materials.