Proposal of an extended t-J Hamiltonian for high-Tc cuprates from ab initio calculations on embedded clusters

摘要

A series of accurate ab initio calculations on CupOq finite clusters, properly embedded in the Madelungpotential of the infinite lattice, have been performed in order to determine the local effective interactions in theCuO2 planes of La22xSrxCuO4 compounds. The values of the first-neighbor interactions, magnetic coupling(JNN5125 meV!, and hopping integral (tNN52555 meV! have been confirmed. Important additional effectsare evidenced, concerning essentially the second-neighbor hopping integral tNNN51110 meV, the displacementof a singlet toward an adjacent colinear hole, hSDabc5280 meV, a non-negligible hole-hole repulsionVNN2VNNN50.8 eV, and a strong anisotropic effect of the presence of an adjacent hole on the values of thefirst-neighbor interactions. The dependence of JNN and tNN on the position of neighbor hole~s! has beenrationalized from the two-band model and checked from a series of additional ab initio calculations. Anextended t-J model Hamiltonian has been proposed on the basis of these results. It is argued that the hereproposedthree-body effects may play a role in the charge/spin separation observed in these compounds, that is,in the formation and dynamic of stripes