Predominance of the multimagnon incoherent component and minuteness of the zero-magnon coherent component in one-body Green’s functions for half-filled Hubbard models
Norikazu Tomita, Keiichirō Nasu
Weights of the multimagnon (incoherent) component and the zero-magnon (coherent) one in the Lehmann's spectral representation of the one-body Green's functions are determined for the one- and the two-dimensional half-filled Hubbard models. The one-body Green's functions with specific momenta are calculated by means of a quantum Monte Carlo simulation. To distinguish the coherent component from the incoherent one in this Lehmann's spectrum, a site-diagonal staggered potential $\ensuremath{\Delta}$ is artificially added to the Hubbard models. Due to this $\ensuremath{\Delta},$ an energy gap opens in the magnon excitation, and as a result, the coherent component is clearly separated from the incoherent one. Systematic analysis on the $\ensuremath{\Delta}$ dependence of these two components shows that the weight of the coherent component is less than a few percent for each dimension in the limit of $\stackrel{\ensuremath{\rightarrow}}{\ensuremath{\Delta}}0,$ which corresponds with the usual Hubbard model. This means that the incoherent component predominates the spectrum, while the coherent component makes only a minute contribution. In contrast to the widely accepted one-electron band picture, our calculations indicate that the so-called lower Hubbard band peak in the photoemission spectrum of the metal-oxide insulator originates mainly from this incoherent component. It does not correspond with the coherent one that reflects a one-electron state.
Physical review. B, Condensed matter•Sep 15, 1999•18 citations