Optical spectra of La2-xSrxCuO4: Effect of carrier doping on the electronic structure of the CuO2 plane

Metallic nonsuperconducting phase and D-wave superconductivity in Zn-substituted La1.85Sr0.15CuO4

Measurements of the resistivity, magnetoresistance, and penetration depth were made on films of La1.85Sr0.15CuO4, with up to 12 at. % of Zn substituted for the Cu. The results show that the quadratic temperature dependence of the inverse square of the penetration depth, indicative of d-wave superconductivity, is not affected by doping. The suppression of superconductivity leads to a metallic nonsuperconducting phase, as expected for a pairing mechanism related to spin fluctuations. The metal-insulator transition occurs in the vicinity of k(F)l approximately 1, and appears to be disorder driven, with the carrier concentration unaffected by doping.

A Basic Electronic Model for the Study of Optical Properties of Delocalized and Partially Localized Donor-Bridge-Acceptor Systems

An electronic model for donor-bridge-acceptor systems is discussed for the specific cases of [(NH(3))(5)Ru-pyz-Ru(NH(3))(5)](m)()(+) and [(NH(3))(5)Ru-(4,4'-bpy)-Ru(NH(3))(5)](m)()(+) (m = 4, 5, 6) as well as for their longer chain analogues. The model accounts for the optical properties observed in the near-IR-vis and provides an explanation of their dependence upon the oxidation state of the metals as well as of the effect of changing the bridging ligand. The results obtained suggest that this model contains the essential ingredients for being considered a basic minimal model for the study of electron transfer in donor-bridge-acceptor systems.

Atomic-Scale Images of the Growth Surface of Ca 1– x Sr x CuO 2 Thin Films

The surface microstructure of c-axis (Ca,Sr)CuO(2) thin films, grown by laser molecular beam epitaxy on SrTiO(3)(001) substrates, was studied by ultrahigh-vacuum scanning tunneling microscopy (STM). Images were obtained for codeposited Ca1-xSrxCuO(2) thin films, which show a layered-type growth mode. The surfaces consist of atomically flat terraces separated by steps that are one unit cell high. A pronounced dependence of the growth mechanism on the Sr/Ca ratio of the films was observed. Atomic resolution STM images of the CuO(2) sheets in the ab plane show a square lattice with an in-plane spacing of 4 angstroms; the lattice contains different concentrations of point defects, depending on the polarity of the sample-tip bias.