Effect of spin structures and nesting on the shape of the Fermi surface and pseudogap anisotropy in the t-t′-U Hubbard models

The effect of two types of spin structures on the shape of the Fermi surface and on the map of photoemission intensities for the t-t'-U Hubbard model is investigated. The stripe phase with a period of 8 a and the spiral spin structure are calculated in the mean field approximation. It is shown that, in contrast to electron-type doping, hole-doped models are unstable to the formation of such structures. Pseudogap anisotropy is different for h- and e-doping and is determined by the spin structure. In accordance with ARPES data for La2-xSrxCuO4, the stripe phase is characterized by quasi-one-dimensional FS segments in the vicinity of points M(+/- pi, 0) and by suppression of the spectral density for k(x) = k(y). It is shown that spiral structures exhibit polarization anisotropy: different segments of the FS correspond to electrons with different spin polarizations. (C) 2004 MAIK "Nauka/Interperiodica".