A Scheme to Combine Dynamical Local and Static Nonlocal Spin Fluctuations

We present a scheme, within either density-functional theory (DFT) or the quasiparticle self-consistent GW (QSGW) approximation, to incorporate nonlocal spin fluctuations in a static approximation. This can be combined with local spin fluctuations computed by a local dynamical theory, e.g. dynamical mean field theory, to yield a high-fidelity description of the one-particle spectrum. As illustrations, we present results for FeSe, Fe(Se,Te) and YFe₂Ge₂ where high-quality ARPES data are available. We further show that DFT can be used to relax structures, and if the local moments are constrained to match moments generated by QSGW, structural properties agree well with experimentally obtained structures, significantly better than structures generated from a nonmagnetic calculation. If time permits, we will present two particle properties (spin susceptibility and superconducting gap functions) with this theory.