Direct observation of the influence of the FeAs4 tetrahedron on   superconductivity and antiferromagnetic correlations in Sr2VO3FeAs
  We measure the pressure dependence of the electrical resistivity and the crystal structure of iron superconductor Sr2VO3FeAs. Below ~10 GPa the structure compresses but remains undeformed, with regular FeAs4 tetrahedrons, and a constant Tc. Beyond 10GPa, the tetrahedron strongly distorts, while Tc goes gradually to zero. Band structure calculations of the undistorted structure show multiple nesting features that hinder the development of an antiferromagnetic ground state (AF), allowing the appearance of superconductivity. The deformation of the tetrahedra that breaks band degeneracy degrades multiple nesting, thus favouring one particular AF state at the expense of Tc. 
Gaston Garbarino, Ruben Weht, Amadou Sow, Claudine Lacroix, Andr\'e   Sulpice, Mohamed Mezouar, Xiyu Zhu, Fei Han, Hai Hu We...
cond-mat.supr-con cond-mat.mtrl-sci