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

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 $\hat{I}\P$ shows a seemingly divergent behavior above the transition temperature $T_0$ and a quick decrease below it. We found that the temperature dependence of $\hat{I}\P$ for both samples can be well described by assuming the uniaxial pressure effect on the gap or certain energy scale except for $\hat{I}{\P }_{(110)}$ 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.

6 pages, 3 figures