Apparatus design for measuring of the strain dependence of the Seebeck coefficient of single crystals.

We present the design and construction of an apparatus that measures the Seebeck coefficient of single crystals under in situ tunable strain at cryogenic temperatures. A home-built three piezostack apparatus applies uni-axial stress to a single crystalline sample and modulates anisotropic strain up to 0.7%. An alternating heater system and cernox sensor thermometry measure the Seebeck coefficient along the uniaxial stress direction. To demonstrate the efficacy of this apparatus, we applied uniaxial stress to detwin single crystals of BaFeAs in the orthorhombic phase. The obtained Seebeck coefficient anisotropy is in good agreement with previous measurements using a mechanical clamp.