Symmetric and antisymmetric strain as continuous tuning parameters for electronic nematic order

TL;DR

This study demonstrates that orthogonal antisymmetric strain is a highly effective continuous tuning parameter for the electronic nematic order in iron pnictides, revealing distinct linear and quadratic responses of the nematic transition temperature.

Contribution

It introduces a method to decompose the effects of symmetric and antisymmetric strains on nematic transition temperature in iron pnictides, highlighting the significance of antisymmetric strain as a tuning parameter.

Findings

Linear response of $T_S$ to symmetric strains quantified.

Quadratic variation of $T_S$ with antisymmetric strains observed.

Antisymmetric strain effects exceed symmetric strain effects by over two orders of magnitude.

Abstract

We report the separate response of the critical temperature of the nematic phase transition $T_{\rm S}$ to symmetric and antisymmetric strains for the prototypical underdoped iron pnictide Ba(Fe$_{0.975}$Co$_{0.025}$)$_2$As$_2$. This decomposition is achieved by comparing the response of $T_{\rm S}$ to uniaxial stress and hydrostatic pressure. In addition to quantifying the two distinct linear responses to symmetric strains, we find a quadratic variation of $T_{\rm S}$ as a response to antisymmetric strains $\epsilon_{\rm B_{1g}}$=$\frac{1}{2}$($\epsilon_{\rm xx}$-$\epsilon_{\rm yy}$), exceeding the non linear response to symmetric strains by at least two orders of magnitude. These observations establish orthogonal antisymmetric strain as a powerful tuning parameter for nematic order.