Response of FeSe to in-plane anisotropic strain

By affixing thin single crystals of FeSe to rigid sample carriers and then applying uniaxial stress to the carrier, we apply in-plane uniaxial strains of up to ~0.7% to FeSe. Above the structural transition temperature T_s, anisotropic strain drives partial polarization of the nematic order, and a corresponding strong resistive anisotropy [1, 2]. However the resistive anisotropy saturates rapidly as strain is applied, and the resistivity then varies nonmonotonically for compressions above ~0.3%. Below T_s, the extrinsic contribution to the resistance from twin boundaries can be identified. The twin boundaries are weakly pinned and can be partially annealed, allowing the intrinsic elastoresistivity below T_s to be resolved.

[1] H.-H. Kuo, J.-H. Chu, J. C. Palmstrom, S. A. Kivelson, and I. R. Fisher, Science 352, 958 (2016).
[2] S. Hosoi et al, Proc. Nat. Acad. Sciences 113, 8139 (2016).