X-ray Diffraction and Transport Study on Single Crystals Ba(Fe_1-xCo_x)₂As₂ Under In-situ Tunable Uniaxial Stress

Underdoped BaFe₂As₂ exhibits both a nematic and antiferromagnetic transition which result in orthorhombic twin domains and an in-plane electronic anisotropy. In the orthorhombic state, uniaxial stress can be used to detwin the system and induce additional lattice distortion. Here we present x-ray diffraction data on crystals under in-situ tunable uniaxial stress, which show a distinct structural response in the tetragonal and fully detwinned single domain orthorhombic phase. This lattice constant data is paired with simultaneous resistivity measurements to compute coefficients in the elastoresistivity tensor within the orthorhombic phase, which cannot be determined from macroscopic strain measurements alone. This work provides a new way to measure nematic susceptibility below the phase transition temperature.