EFFECTIVE ONE-BAND ELECTRON-PHONON HAMILTONIAN FOR NICKEL PEROVSKITES

Inspired by recent experiments on the Sr-doped nickelates, La{sub 2{minus}x}Sr{sub x}NiO{sub 4}, we propose a minimal microscopic model capable of describing the variety of the observed quasistatic charge/lattice modulations and the resulting magnetic and electronic-transport anomalies. Analyzing the motion of low-spin (s=1/2) holes in a high-spin (S=1) background as well as their coupling to the in-plane oxygen phonon modes, we construct a sort of generalized Holstein t-J Hamiltonian for the NiO{sub 2} planes, which contains, besides the rather complex {open_quotes}composite-hole{close_quotes} hopping part, nonlocal spin-spin and hole-phonon interaction terms. {copyright} {ital 1997} {ital The American Physical Society}