Role of disorder and strong 5d electron correlation in the electronic structure of Sr2TiIrO6

Abstract

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.