Quasiparticle states of the Hubbard model near the Fermi level

TL;DR

This paper investigates the quasiparticle spectra of the Hubbard model near the Fermi level, revealing persistent four-band structures and the emergence of a narrow quasiparticle band with doping, leading to pseudogap formation.

Contribution

It demonstrates that the four-band structure persists beyond half-filling and identifies a new narrow quasiparticle band near the Fermi level with doping.

Findings

Four-band structure persists with doping

A narrow quasiparticle band appears near the Fermi level with doping

Pseudogap forms as spectral intensities decrease near the Fermi level

Abstract

The spectra of the t-U and t-t'-U Hubbard models are investigated in the one-loop approximation for different values of the electron filling. It is shown that the four-band structure which is inherent in the case of half-filling and low temperatures persists also for some excess or deficiency of electrons. Besides, with some departure from half-filling an additional narrow band of quasiparticle states arises near the Fermi level. The dispersion of the band, its bandwidth and the variation with filling are close to those of the spin-polaron band of the t-J model. For moderate doping spectral intensities in the new band and in one of the inner bands of the four-band structure decrease as the Fermi level is approached which leads to the appearance of a pseudogap in the spectrum.