Optical investigation of the metal-insulator transition in the Ca-free Pb2Sr2LCu3O8 (L=Y, Dy, Eu, Sm, Nd, and Pr) series

The ab-plane dc resistivity and reflectivity of single crystals of the Ca-free Pb2Sr2LCu3O8 series, where L=Y, Dy, Eu, Sm, Nd, and Pr, has been investigated. A trend is observed from insulating to metallic and superconducting behavior with decreasing size of the rare-earth constituent. A transfer of spectral weight from the Cu-O charge-transfer band to the mid- and far-infrared regions accompanies the progression to metallic character. As the …