SPECTRAL-FUNCTION OF SMALL SPIN POLARON IN 2-DIMENSIONAL SPHERICALLY SYMMETRICAL ANTIFERROMAGNETIC STATE

The spectral density A(p)(k,omega) of a small spin polaron in the CuO2 plane is calculated in the self-consistent Born approximation within the framework of the three-band model. It is shown that the spin polar on is a good quasiparticle excitation for this model. A(p)(k,omega) de monstrates small damping in contrast to A(h)(k,omega) for a bare hole, and the lowest boundary omega(p,min) of A(p)(k, omega) lies much lowe r than omega(?)(h,min) for A(h)(k, omega). The quasiparticle peak disp ersion reproduces the flat region near the band bottom that is charact eristic of the bare polaron spectrum Omega(k). The spherically symmetr ic approach is used for description of spin excitations. It makes it p ossible to consider the quantum antiferromagnetic background without t he spontaneous symmetry breaking and the unit cell doubling.