Optical Absorption of YBa2Cu3O7-δ and ErBa2Cu3O7-δ Crystals due to Interband Transition

Abstract
Reflectivity in the a-b plane of single crystals of orthorhombic YBa2Cu3O7-δ and ErBa2Cu3O7-δ has been measured at room temperature in the photon energy region from 0.05 to 30 eV and the spectra of absorption and energy loss function have been obtained by the Kramers-Kronig analysis. General features of the structure in the spectra of the Y-compound in the interband transition region from 1 to 8 eV are consistent with those calculated by Zhao et al. based on the energy band theory, but peaks in the observed absorption spectrum are shifted by 1 to 2 eV to the high energy side compared with the calculation.