Quasiparticle broadening in insulating copper oxides

We calculate the spectral function of the half-filled two-dimensional Hubba rd model with realistic hopping integrals for Sr2CuO2Cl2 within the dynamic al mean-field theory at finite temperatures. It is shown that precursor eff ects of incommensurate spin dynamics lead to an incoherent broadening of th e quasiparticle peaks on an energy scale that depends on local spin order. This might serve as an indirect method of detecting changes of local spin o rder under doping. (C) 1999 Elsevier Science B.V. All rights reserved.