High-T ^c superconductivity in the LaFeAsO _1-xF _x system based on inelastic neutron scattering measurements

Dynamical spin susceptibility ^χ″(q,ω) of the LaFeAsO _1-xF _x system is discussed based on the itinerant picture. The spin resonant energy relative to the superconducting transition temperature is compared with those of other iron-based superconductors, and discussed in relation to the anomalous phonon mode of Y Ni ₂B ₂C. Phase diagrams of iron-based and copper oxide superconductors are discussed in terms of chemical bonding characters. Possible lattice breathing by the electron round scattering between hole and electron Fermi surfaces is proposed from the chemical point of view.