"Elastoresistive and elastocaloric anomalies at magnetic and electronic-nematic critical points"

Alexander T. Hristov: Matthias S. Ikeda, Johanna C. Palmstrom, Philip Walmsley, and Ian R. Fisher; Physical Review B, 03/11/19.

Additional Authors: Matthias S. Ikeda, Johanna C. Palmstrom, Philip Walmsley, and Ian R. Fisher

Abstract:

Using Ba(Fe0.975Co0.025)2As2 as an exemplar material exhibiting second-order electronic-nematic and antiferromagnetic transitions, we present measurements that reveal anomalies in the elastoresistance (∂ρij/∂ɛkl) and elastocaloric effect (∂T/∂ɛkl) at both phase transitions for induced strains ɛkl that do not share the symmetry of either order parameter. Both effects are understood to arise from the effect of strain on the transition temperatures; in the region close to the phase transitions this leads to (1) similarity between the strain and temperature derivatives of the resistivity and (2) similarity between the elastocaloric effect and the singular part of the specific heat. These mechanisms for elastoresistance and elastocaloric effect should be anticipated for any material in which mechanical deformation changes the transition temperature. Furthermore, these measurements provide evidence that the Fisher-Langer relation ρ(c)∝U(c) between the scattering from critical degrees of freedom and their energy density, respectively, holds near each of the transitions in the material studied under varying strain as it does for varying temperature.