Spin dynamics in electron-doped pnictide superconductors

TL;DR

This study models spin excitations in electron-doped Ba(Fe$_{1-x}$Co$_{x}$)$_{2}$As$_{2}$ superconductors, revealing doping-dependent behaviors and pseudogap phenomena consistent with experimental observations.

Contribution

It introduces a two-orbital RPA model that captures the doping dependence of spin excitations and the pseudogap behavior in electron-doped pnictide superconductors.

Findings

Spin susceptibility matches neutron scattering data across doping levels.

Overdoped samples show a pseudogap-like behavior in spin susceptibility.

The model explains the interplay between SDW and superconductivity.

Abstract

The doping dependence of spin excitations in Ba(Fe$_{1-x}$Co$_{x}$)$_{2}$As$_{2}$ is studied based on a two-orbital model under RPA approximation. The interplay between the spin-density-wave (SDW) and superconductivity (SC) is considered in our calculation. Our results for the spin susceptibility are in good agreement with neutron scattering (NS) experiments in various doping ranges at temperatures (T) above and below the superconducting transition temperature T$_{c}$. For the overdoped sample where one of the two hole pockets around $\Gamma$ point disappears according to ARPES, we show that the imaginary part of the spin susceptibility in both SC and normal phases exhibits a gap-like behavior. This feature is consistent with the "pseudogap" as observed by recent NMR and NS experiments.