Abstract
Doping dependence of the spin fluctuations and the electron correlations in the effective five-band Hubbard model for iron pnictides is investigated using the fluctuation-exchange approximation. For a moderate hole doping, we find a dominant low-energy spin excitation at , which becomes critical at low temperature. The low-energy spin excitations in the heavily hole-doped region are characterized by weak dependence. The electron doping leads to an appearance of a pseudogap in spin-excitation spectrum. Correspondingly, the NMR- relaxation rate is strongly enhanced on the hole-doped side and suppressed on the electron-doped side of the phase diagram. This behavior can be to large extent understood by systematic changes of the Fermi-surface topology.
- Received 23 February 2010
DOI:https://doi.org/10.1103/PhysRevB.82.024508
©2010 American Physical Society