Doping dependence of spin fluctuations and electron correlations in iron pnictides

TL;DR

This study investigates how doping affects spin fluctuations and electron correlations in iron pnictides using a five-band Hubbard model, revealing doping-dependent changes in spin excitation spectra and NMR relaxation rates.

Contribution

It provides a systematic analysis of doping effects on spin excitations and electron correlations in iron pnictides within a five-band Hubbard model using fluctuation-exchange approximation.

Findings

Low-energy spin excitation at Q=(π,0) dominates at moderate hole doping.

Heavily hole-doped regions show weak Q dependence in spin excitations.

Electron doping induces a pseudogap in the spin excitation spectrum.

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 Q=(\pi,0), which becomes critical at low temperature. The low-energy spin excitations in the heavily hole-doped region are characterized by weak Q dependence. The electron doping leads to an appearance of a pseudogap in spin excitation spectrum. Correspondingly, the NMR-1/T1 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.