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

TL;DR

This study investigates how disorder and strong 5d electron correlations influence the electronic and magnetic properties of Sr2TiIrO6, revealing complex interactions including electron-electron and electron-magnon couplings, and a disorder-driven insulator transition.

Contribution

It demonstrates the necessity of considering spin-orbit coupling and electron correlation to understand the electronic structure of disordered Sr2TiIrO6, highlighting the interplay of disorder, correlations, and magnetic order.

Findings

Insulator to insulator transition at 240 K with magnetic transition

Spectral density shows |E-E_F|^2 dependence at room temperature

Below magnetic transition, spectral density follows |E-E_F|^{3/2}

Abstract

Transport and magnetic properties along with high resolution valence band photoemission study of disordered double perovskite Sr$_{2}$TiIrO$_{6}$ has been investigated. Insulator to insulator transition along with a magnetic transition concurrently occurs at 240 K. Comparison of valence band photoemission with band structure calculations suggests that the spin orbit coupling as well as electron correlation are necessary to capture the line shape and width of the Ir 5$d$ band. Room temperature valence band photoemission spectra show negligibly small intensity at Fermi energy, $E_{F}$. Fermi cut-off is observed at low temperatures employing high resolution. The spectral density of states at room temperature exhibits $|E-E_{F}|^{2}$ energy dependence signifying the role of electron-electron interaction. This energy dependence changes to $|E-E_{F}|^{3/2}$ below the magnetic transition evidencing the role of electron-magnon coupling in magnetically ordered state. The evolution of pseudogap ($\pm$12 meV) explains the sudden increase in resistivity ($\rho$) below 50 K in this disordered system. The temperature dependent spectral density of states at $E_{F}$ exhibiting $T^{1/2}$ behaviour verifies Altshuler-Aronov theory for correlated disordered systems.