Evidence for a nematic component to the hidden-order parameter in URu2Si2 from differential elastoresistance measurements

For materials that harbour a continuous phase transition, the susceptibility of the material to various fields can be used to understand the nature of the fluctuating order and hence the nature of the ordered state. Here we use anisotropic biaxial strain to probe the nematic susceptibility of URu 2 Si 2 , a heavy fermion material for which the nature of the low temperature ‘hidden order’ state has defied comprehensive understanding for over 30 years. Our measurements reveal that the fluctuating order has a nematic component, confirming reports of twofold anisotropy in the broken symmetry state and strongly constraining theoretical models of the hidden-order phase. The heavy fermion material URu 2 Si 2 exhibits a hidden-order phase transition that remains poorly understood. Using differential elastoresistance measurements, Riggs et al . show that this phase has a nematic component and that it spontaneously breaks fourfold lattice symmetry.