Theoretical description of charge excitations in low-dimensional undoped cuprates

Institut für Theoretische Physik, Technische Universität Dresden D-01062 Dresden, Germany

Received: 25 January 1999
Accepted: 20 April 1999

Abstract

We investigate Cu X-ray photoemission spectra of low-dimensional undoped cuprates within a multi-band Hubbard model, using a cumulant projection technique. This method makes the treatment of infinite systems possible while still allowing for a clear interpretation of final states. Delocalization processes and multiplet splitting are described within one framework. The results are compared to those of exact diagonalization calculations and to experimental spectra of Bi₂CuO₄ and Sr₂CuO₃. For both compounds the calculations are in good agreement with the experiment. The charge-transfer energy Δ for Sr₂CuO₃ is found to be smaller than in other cuprates.