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In this work, we have investigated the precursor effects to superconductivity in BaPb0.75Bi0.25O3 using temperature dependent resistivity, x-ray diffraction technique and photoemission spectroscopy. The present compound exhibits superconductivity around 11 K (TC). The synthesis procedure adopted is much simpler as compared to the procedure available in the literature. In the temperature range (10 K–25 K) i.e. above TC, our results show an increase in both the orthorhombic and tetragonal strain. The well screened features observed in Bi and Pb 4f7/2 core levels are indicative of the metallic nature of the sample. The compound exhibits finite intensity at the Fermi level at 300 K and this intensity decreases with decrease in temperature and develops into a pseudogap; the energy dependence of the spectral density of states suggests disordered metallic state. Furthermore, our band structure calculations reveal that the structural transition upon Pb doping results in the closing of the band gap at the Fermi level.closing of the band gap at the Fermi level.

Electronic and magnetic properties of the new 120 K Tl-Ca-Ba-Cu-O superconductor are presented. Resistance-temperature variations, ac susceptibility, and the (low) magnetic field dependence of the critical current density are reported. The new superconductor can be prepared in a molten state, which should allow processing leading to high critical current density. Preliminary x-ray diffraction data are also presented.

Transport and magnetic properties along with a high-resolution valence band photoemission study of disordered double perovskite Sr2TiIrO6have been investigated. The insulator to insulator transition along with a magnetic transition concurrently occur at 240 K. The comparison of the valence band photoemission with band structure calculations suggests that the spin orbit coupling as well as the electron correlation are necessary to capture the line shape and width of the Ir 5d band. Room temperature valence band photoemission spectra show a negligibly small intensity at the Fermi energy, EF. A Fermi cut-off is observed at low temperatures employing high resolution. The spectral density of states at room temperature exhibits energy dependence signifying the role of electron-electron interaction. This energy dependence changes to below the magnetic transition evidencing the role of the electron-magnon coupling in a magnetically ordered state. The evolution of a pseudogap () explains the sudden increase in resistivity below 50 K in this disordered system. The temperature-dependent spectral density of states at EF exhibiting behaviour verifies the Altshuler-Aronov theory for correlated disordered systems.