Title: Evolution of Anisotropic Displacement Parameters and Superconductivity with Chemical Pressure in BiS2-Based REO0.5F0.5BiS2 (RE = La, Ce, Pr, and Nd),
Abstract: In order to understand the mechanisms behind the emergence of
superconductivity by the chemical pressure effect in REO0.5F0.5BiS2 (RE = La,
Ce, Pr, and Nd), where bulk superconductivity is induced by the substitutions
with a smaller-radius RE, we performed synchrotron powder X-ray diffraction,
and analyzed the crystal structure and anisotropic displacement parameters.
With the decrease of the RE3+ ionic radius, the in-plane disorder of the S1
sites significantly decreased, very similar to the trend observed in the
Se-substituted systems: LaO0.5F0.5BiS2-xSex and Eu0.5La0.5FBiS2-xSex.
Therefore, the emergence of bulk superconductivity upon the suppression of the
in-plane disorder at the chalcogen sites is a universal scenario for the
BiCh2-based superconductors. In addition, we indicated that the amplitude of
vibration along the c-axis of the in-plane chalcogen sites may be related to
the Tc in the BiCh2-based superconductors.