Figure 1: Measurement of elastoresistivity coefficients.
Anisotropic strain is achieved by gluing thin crystals of URu2Si2 to the side of a PZT piezoelectric stack such that εxx is opposite in sign to εyy. The Cartesian axes are defined relative to the piezo stack itself, with the x-(y-)direction parallel to the short (long) axis of the piezo. (a) Photograph of [100] oriented URu2Si2 crystals mounted in the (ΔR/R)yy and (ΔR/R)xx directions on the surface of a PZT piezoelectric stack. Strain gauges mounted on the opposite face of the piezo stack measure εyy and εxx, which are related by the effective Poisson ratio of the PZT stack, νp≡−εxx/εyy. (b) and (c) show representative (ΔR/R)yy elastoresistance data for five different temperatures as a function of εyy for 
and [100] orientations, respectively. Data are plotted for both warming and cooling cycles and are identical within the resolution of the experiment. The resistive response to anisotropic strain is considerably larger (by a factor of ~4) for measurements made in the 
direction compared with the [100] direction.
