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.

Revelation of Mott insulating state in layered honeycomb lattice Li$_2$RuO$_3$

“…here in the high resolution He I spectra. The parabolic energy dependence of spectral DOS manifests strong correlation induced soft Coulomb gap at E in this finitely disordered system [14,26,45].…”

“…2(a) that the O 2p and Ru 4d bands are distinctly separated in high and low excitation energy spectra. Thus, Ru 4d contributions can reliably be delineated by fitting O 2p bands using two Gaussians representing feature B and C as performed in other systems [14,19,21,26]. Lines in Fig.…”

“…Ru doped Li 2 IrO 3 demonstrates that models based on the assumption of only SOC do not describe this system properly [9]. In addition to SOC, onsite electron correlation (U ) among d electrons is also expected to play an important role, as found in relativistic Mott insulator Na 2 IrO 3 [10] as well as in many other transition metal oxides [11][12][13][14]. On-site electron correlation and its role in deciding the novel ground state properties have been extensively studied in TMOs [15] where the systems can be defined by a single parameter U /W (W = width of the d band) within the Mott-Hubbard model and the Mott criteria U /W ∼ 1 separates the Mott insulators (U /W ¿ 1) and correlated metals (U /W ¡ 1) [16,17].…”

Revelation of Mott insulating state in layered honeycomb lattice Li2RuO3

“…Ru doped Li 2 IrO 3 demonstrates that models based on the assumption of only SOC do not describe this system properly [9]. In addition to SOC, onsite electron correlation (U) among d electrons is also expected to play an important role, as found in relativistic Mott insulator Na 2 IrO 3 [10] as well as in many other TMOs [11][12][13][14]. On-site electron correlation and its role in deciding the novel ground state properties have been extensively studied in TMOs [15] where the systems can be defined by a single parameter U/W (W = width of the d band) within the Mott-Hubbard model and the Mott criteria U/W ∼ 1 separates the Mott insulators (U/W > 1) and correlated metals (U/W < 1) [16,17].…”

Electron correlation effect versus spin–orbit coupling for tungsten and impurities

“…However, a study of Osmium reveals that the inclusion of the electron correlation between 5d electrons correctly predicted the electronic topological transition of the system under pressure and cannot be neglected [15,16]. Reddy et al also emphasized the strong 5d electron correlation in their work [17]. On another hand, recently Jiang et al have developed a fast and rather accurate method to evaluate the Coulomb interaction strengths self-consistently through first principles calculations based on some approximations [18].…”