Local structural distortions and their role in superconductivity in   SmFeAsO$_{1-x}$F$_x$ superconductors
  EXAFS studies at the As K edge as a function of temperature have been carried out in SmFeAsO$_{1-x}$F$_x$ ($x$ = 0 and 0.2) compounds to understand the role of local structural distortions superconductivity observed in F doped compound. A significant correlation between thermal variation of local structural parameters like anion height and superconducting onset is found in the fluorinated compound. Such a variation in anion height is absent in non-superconducting compound. Increase in Fe-As bond distance just below superconducting onset temperature indicates a similarity in distortions observed in high T$_C$ cuprates and these Fe based superconductors. 
Kapil Ingle, K.R. Priolkar, Anand Pal, V. P. S. Awana and S. Emura
cond-mat.supr-con