double exchange relevant for High Tc superconductivity

Last year there published a paper [Hai-Yao Deng 2009 J. Phys.: Condens. Matter 21 075702] in which a model was proposed to address the issues regarding the coexistence of Zhang-Rice singlet formation and the spin glass at very low doping in cuprates. This model contains not only itinerant charges but also localized spins. There is strong on-site anti-ferromagnetic coupling between them. This coupling is held responsible for the formation of ZRS and the formation of spin glass, as a result of double exchange. Now there came very latest studies [Phys. Rev. B 82, 045125 (2010);Phys. Rev. Lett. 105, 107004 (2010)] that held similar ideas in solving puzzles residing in iron-based pnictides. This should not be regarded as a simple coincidence. It may strengthen the idea that, high Tc SC is intimately connected with magnetic fluctuations. More likely, this model may serve as a unification for High Tc superconductors of both iron-based and copper-based.