BRINKMAN-RICE TRANSITION DRIVEN BY INTERATOMIC REPULSION IN HEXAGONAL COPPER OXIDES

We propose an effective one-band Hamiltonian to describe the low-energy physics of RCuO2+δ delafossites, assuming that the relevant states are predominantly Cu 3d3z2-r2 and O pz. Due to geometrical factors, the effective hopping between Cu sites is nearly 16 times smaller than in superconducting cuprates. As a consequence, when the effective Hamiltonian is treated in slave-boson mean-field theory, a moderate interatomic repulsion drives a localization transition in the structure proposed for oxygen content 8/3. Experimental evidence suggests that La2CuO2.66 and Y0.99Ca0.01CuO2.66 are near the localization transition but on opposite sides of it. © 1995 The American Physical Society.