Normal-state pseudogap and electron flat dispersion in copper oxide materials

The anomalous momentum and doping dependence of the electron spectral funct ion and electron dispersion for copper oxide materials in the underdoped re gime are studied within the t-J model. It is shown that the electron spectr um is changed with dopings, and the electron dispersion exhibits a flat ban d around the (pi,0) point in the Brillouin zone, which leads to the normal- state pseudogap formation. The theoretical results are consistent with expe riments and numerical simulations. (C) 2000 Elsevier Science B.V. All right s reserved.