Cu-O network dependence of optical charge-transfer gaps and spin-pair excitations in single-CuO2-layer compounds

Abstract

Spectra of optical conductivity and magnon Raman scattering have been investigated in single crystals of a parent family of cuprate superconductors with various types of Cu-O single-layer networks. The analysis of the spectra shows the systematic dependence of the charge-transfer gaps and covalent character of Cu-O bonds on the pattern of the Cu-O network, while the spin-exchange energy is rather convergent for all the single-${\mathrm{CuO}}_2$-sheet compounds.