Evolution of the Band Structure of Quasiparticles
with Doping in Copper Oxides on the Basis
of a Generalized Tight-Binding Method

V. A. Gavrichkov*, S. G. Ovchinnikov, A. A. Borisov, and E. G. Goryachev

Kirenskii Institute of Physics, Siberian Division, Russian Academy of Sciences, Krasnoyarsk, 660036 Russia

*e-mail: gav@ksc.krasn.ru

Received January 18, 2000

Abstract—Two methods for stabilizing the two-hole ³B_1g state as the ground state instead of the Zhang–Rice
singlet are determined on the basis of an orthogonal cellular basis for a realistic multiband pd model of a CuO₂
layer and the dispersion relations for the valence band top in undoped and doped cases are calculated. In the
undoped case, aside from the valence band, qualitatively corresponding to the experimental ARPES data for
Sr₂CuO₂Cl₂ and the results obtained on the basis of the t–t'–J model, the calculations give a zero-dispersion vir-
tual level at the valence band top itself. Because of the zero amplitude of transitions forming the virtual level
the response corresponding to it is absent in the spectral density function. In consequence, the experimental
ARPES data do not reproduce its presence in this antiferromagnetic undoped dielectric. A calculation of the
doped case showed that the virtual level transforms into an impurity-type band and acquires dispersion on
account of the nonzero occupation number of the two-hole states and therefore should be detected in ARPES
experiments as a high-energy peak in the spectral density. The computed dispersion dependence for the valence
band top is identical to the dispersion obtained by the Monte Carlo method, and the ARPES data for optimally
doped Bi₂Sr₂CaCu₂O₈₊ samples. The data obtained also make it possible to explain the presence of an energy
pseudogap at the symmetric X point of the Brillouin band of HTSC compounds. © 2000 MAIK “Nauka/Inter-
periodica”.

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