Abstract: Transition metal compounds have a strong tendency to be a Mott insulator or remain close to it and develop local moments. Iron Arsenide superconductor family is no exception. In this family, tendency to form a Fe spin-1 moment is apparent in the phenomenology.
A recent striking example is the vacancy ordered K_2Fe_4Se_5, where Fe exhibits spin-2 moment. It is believed that this system has coexisting antiferromagetism (T_N ~ 600 K) and superconductivity (T_c ~ 30 K). Further, Fe based superconductors are similar in many ways to Cuprates and Organic superconductors. Putting all these together, we will present a strong coupling perspective [1,2] for magnetism and superconductivity in Fe based superconductors. In our theory, a reference Mott insulator, which is either externally doped or self doped (due to chemical pressure) plays a fundamental role. A striking consequences of our our theory is that it offers scope for higher superconducting Tc's, competing with cuprates.
[1] G. Baskaran, J. Phys. Soc. Jap., vol.77 page 113713 (2008)
[2] G. Baskaran, arXiv:1108.3562
