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TT: Fachverband Tiefe Temperaturen

TT 20: Correlated Electrons - Poster Session

TT 20.67: Poster

Mittwoch, 28. März 2007, 14:00–17:45, Poster A

Pseudogap and the spin-polaron band in the Hubbard model — •Alexei Sherman¹ and Michael Schreiber² — ¹Institute of Physics, University of Tartu, 51014 Tartu, Estonia — ²Institut für Physik, Technische Universität, D-09107 Chemnitz, Germany

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.