FREE AND SPIN-POLARON STATES IN HIGH T_C SUPERCONDUCTORS

摘要

Hole states in the antiferromagnetically ordered CuO_2 planes of cupra-te perovskites are calculated within the three-band Hubbard model and with a self-consistent calculation of the Cu spin polarization. It is found that in the low doping limit the spin-polaron and the free-hole states are separated by a barrier of energy ～ 0.05eV. At finite dopings the spin-polaron states become less favorable and at high doping they turn out to be metastable. In case of high mobility of donors a phase separation of the charge carriers into domains with a local hole concentration c ～ 0.5 takes place. This explains experimentally observed formation of stripe domains with local hole concentrations c = 0.5.