Plasma Spectra of New Superconductors (La1-xAx)2CuO4

Abstract
The optical reflectivity spectra of new superconductors (La1-x M x )2CuO4 (M=Ba, Ca, Sr) were investigated. In the spectra for the metallic samples, a plasma edge was observed at almost the same position for all compositions x and for all substituents. Based on the two-dimensional tight-binding model, the conduction band width was estimated to be about 1 eV from the value of the observed plasma energy.