OPTICAL REFLECTIVITY SPECTRA OF SINGLE-CRYSTAL BI2SR2CAN-1CUNO2N+4+X (N=1 AND 2)

The optical reflectivity spectra of the single-crystal Bi-based cuprates, Bi2Sr2CaCu2O8+x and Bi2Sr2CuO6+x, were measured in a wide energy range from 0.05 to 40 eV, and analyzed through the Kramers-Kronig relation. The obtained spectra are different from other superconducting cuprates, such as (La,Sr)2CuO4 and YBa2Cu3Ox, which might be ascribed to the existence of the characteristic Bi2O2 layer. The optical excitations within Bi2O2 layer start from 2 eV or higher energy, so it is unlikely that the electrons in the Bi2O2 layer contribute to low-energy excitation or dc conduction in this family of high-Tc superconductors. © 1990 The American Physical Society.