In-plane anisotropic response to the uniaxial pressure in the hidden order state of URu$_2$Si$_2$

TL;DR

This study investigates how uniaxial pressure affects resistivity in URu2Si2, revealing in-plane anisotropic responses in the hidden order phase that do not break lattice symmetry, and compares it with the antiferromagnetic phase.

Contribution

It provides new insights into the anisotropic uniaxial pressure response in the hidden order state of URu2Si2, highlighting differences from the antiferromagnetic phase.

Findings

Elastoresistivity shows divergence above transition temperature

In-plane anisotropic response exists in the hidden order phase

Residual elastoresistivity at 0 K in certain directions

Abstract

We studied the uniaxial-pressure dependence of the resistivity for URu$_{2-x}$Fe$_x$Si$_2$ samples with $x$ = 0 and 0.2, which host a hidden order (HO) and a large-moment antiferromagnetic (LMAFM) phase, respectively. For both samples, the elastoresistivity $\zeta$ shows a seemingly divergent behavior above the transition temperature $T_0$ and a quick decrease below it. We found that the temperature dependence of $\zeta$ for both samples can be well described by assuming the uniaxial pressure effect on the gap or certain energy scale except for $\zeta_{(110)}$ of the $x$ = 0 sample, which exhibits a non-zero residual value at 0 K. We show that this provides a qualitative difference between the HO and LMAFM phases. Our results suggest that there is an in-plane anisotropic response to the uniaxial pressure that only exists in the hidden order state without necessarily breaking the rotational lattice symmetry.