Schrieffer‐Wolff Transformation of the p–d Model for Oxide Superconductors Charge Fluctuation Regime

To describe low‐energy properties of the CuO 2 plane in oxide superconductors the effective interactions up to the fourth order in the p–d hybridization amplitude, V , are derived systematically by the Schrieffer‐Wolff transformation. Contrary to other analogous derivations the value of V is assumed to be comparable to the charge transfer gap, V ≈ Δ = ϵ p − ϵ p , that corresponds to the charge fluctuation (not spin fluctuation, V < Δ) regime in the system. Among the variety of relevant phenomena only a particular problem of magnetic frustrations in the system of Cu‐spins is examined.