Temperature-dependent local structure and superconductivity of BaPd2As2 and SrPd2As2

Abstract

The local structures of 122-type paradium arsenides, namely BaPd 2 As 2 and SrPd 2 As 2 , are examined by As Kedge extended x-ray absorption fine structure measurements to find a possible correlation between the variation of their superconducting transition temperature and the local structure. The local atomic distances are found to be consistent with average distances measured by diffraction techniques. The temperature dependence of mean square relative displacements reveal that, while BaPd 2 As 2 is characterized by a local As-Pd soft mode, albeit with larger atomic disorder, SrPd 2 As 2 shows anomalous As-Pd correlations with a kink at ∼160 K due to hardening by raising temperature. We have discussed implications of these results and possible mechanisms of differing superconducting transition temperature in relation with the structural instability.

Electronic and lattice structure of CaFe1−xCoxAsF probed by x-ray absorption spectroscopy

“…Local lattice structure is closely related to band splitting and thus can give valuable information on the band structure of such compounds. X-ray absorption spectroscopy as a powerful tool to investigate the local lattice structure, has been widely utilized to probe the local electronic and lattice structures of several different types of Fe-based superconductors such as REFeAsO 1−x F x (RE=La, Sm, Nd, Pr, etc) and BaFe 2 As 2 [20][21][22][23][24][25]. However, the investigations of the local lattice and electronic structure of CaFeAsF and Fe(Te,Se) by means of x-ray absorption spectroscopy measurements are still rare.…”