Implications of the Measured Angular Anisotropy at the Hidden Order Transition of URu2Si2

TL;DR

This paper investigates the angular anisotropy of susceptibility in URu2Si2 near its hidden order transition, revealing intrinsic Ising anisotropy that persists above the transition, with implications for understanding the order parameter.

Contribution

It provides new insights into the anisotropic nature of the hidden order parameter and its extension above the transition temperature through susceptibility measurements.

Findings

Order parameter has intrinsic Ising anisotropy.

Anisotropy extends above the hidden order transition.

Susceptibility measurements suggest spin fluctuation anisotropy.

Abstract

The heavy fermion compound URu2Si2 continues to attract great interest due to the long- unidentified nature of the hidden order that develops below 17.5K. Here we discuss the implications of an angular survey of the linear and nonlinear susceptibility of URu2Si2 in the vicinity of the hidden order transition. While the anisotropic nature of spin fluctuations and low-temperature quasiparticles was previously established, our recent results suggest that the order parameter itself has intrinsic Ising anisotropy, and that moreover this anisotropy extends far above the hidden order transition. Consistency checks and subsequent questions for future experimental and theoretical studies of hidden order are discussed.