Measurement of Elastoresistivity at Finite Frequency by Amplitude Demodulation

TL;DR

This paper introduces an AC strain-based method for elastoresistivity measurements, enabling faster, less invasive, and more temperature-stable characterization of materials, demonstrated on an iron-based superconductor.

Contribution

The work presents a novel AC elastoresistivity measurement technique that improves speed and stability over traditional DC methods, and explores the frequency independence of elastoresistivity.

Findings

AC elastoresistivity measurements are consistent with DC results.

The method works effectively between 10 Hz and 3 kHz.

Dynamic elastoresistivity is a distinct, frequency-independent property.

Abstract

Elastoresistivity, the relation between resistivity and strain, can elucidate subtle properties of the electronic structure of a material and is an increasingly important tool for the study of strongly correlated materials. To date, elastoresistivity measurements have been predominantly performed with quasi-static (DC) strain. In this work, we demonstrate a method for using AC strain in elastoresistivity measurements. A sample experiencing AC strain has a time-dependent resistivity, which modulates the voltage produced by an AC current; this effect produces time-dependent variations in resisitivity that are directly proportional to the elastoresistivity, and which can be measured more quickly, with less strain on the sample, and with less stringent requirements for temperature stability than the previous DC technique. Example measurements between 10 Hz and 3 kHz are performed on a material with a large, well-characterized and temperature dependent elastoresistivity: the representative iron-based superconductor BaFe$_{1.975}$Co$_{0.025}$As$_2$. These measurements yield a frequency independent elastoresistivity and reproduce results from previous DC elastoresistivity methods to within experimental accuracy. We emphasize that the dynamic (AC) elastoresistivity is a distinct material-specific property that has not previously been considered.