One-body Green function of half-filled Hubbard model predominated by multi-magnon incoherent component

Abstract

We show that for one- and two-dimensional half-filled Hubbard models, multi-magnon incoherent component predominates the Lehmann spectrum of the one-body Green function, while zero-magnon coherent component only makes a minute contribution. To distinguish the coherent component from the incoherent one, we add a site-diagonal staggered potential Δ to the usual Hubbard model. This Δ artificially opens a finite energy gap in a magnon excitation, and as a result, the zero-magnon coherent component is clearly separated from the multi-magnon incoherent one. Systematic analysis on Δ-dependence of these two components shows that the weight of the coherent component is less than a few percent in the limit of Δ→0. Our results indicate that a peak in the angle-resolved photoemission spectrum of an insulator driven by the strong Coulomb repulsion originates mainly from this incoherent component. It does not reflect a one-body state.