The electronic structure of the high-symmetry perovskite iridate Ba2IrO4

S Moser,E Rotenberg,M Isobe,H Okabe,K S Kim,V V Mazurenko,A Ebrahimi,M Grioni,J Akimitsu,H M Rønnow,B Dalla Piazza,A Bostwick,J Chang,L Moreschini

doi:10.1088/1367-2630/16/1/013008

Abstract

We report angle-resolved photoemission (ARPES) measurements, density functional and model tight-binding calculations on Ba2IrO4 (Ba-214), an antiferromagnetic (TN = 230 K) insulator. Ba-214 does not exhibit the rotational distortion of the IrO6 octahedra that is present in its sister compound Sr2IrO4 (Sr-214), and is therefore an attractive reference material to study the electronic structure of layered iridates. We find that the band structures of Ba-214 and Sr-214 are qualitatively similar, hinting at the predominant role of the spin–orbit interaction in these materials. Temperature-dependent ARPES data show that the energy gap persists well above TN, and favor a Mott over a Slater scenario for this compound.

Highlights

The iridates are a new family of strongly correlated materials, with fascinating physical properties [1,2,3,4,5,6,7,8,9,10,11,12]
Unlike 3d transition metal oxides (TMOs), dominated by the Coulomb interaction, or 4d TMOs, where Hund’s rule coupling plays a major role [13], the electronic structure of the 5d iridates reflects the coexistence of similar Coulomb, crystal-field (CEF) and spin–orbit (SO) coupling energy scales
The electronic structure is shaped by strong SO coupling, which splits the Ir 5d t25g manifold, so that the highest occupied state is a narrow, half-filled jeff = 1/2 band

Summary

Introduction

The iridates are a new family of strongly correlated materials, with fascinating physical properties [1,2,3,4,5,6,7,8,9,10,11,12]. The layered perovskite Sr2IrO4 (Sr-214) has attracted considerable attention because of intriguing similarities with the cuprate parent compound La2CuO4 (LCO). It exhibits weakly coupled IrO2 square-lattice planes built from corner-sharing IrO4 plaquettes, analogous to the characteristic CuO4 building blocks of the cuprates [4, 5, 14,15,16]. Due to the larger Ba radius, Ba-214 does not exhibit the rotational distortion, and is a more promising parent compound for possible iridate superconductors. ARPES data collected over a broad temperature range do not give evidence for a temperaturedependent gap, and are more consistent with a Mott than with a Slater scenario

Methods

Band structure

Temperature evolution

First-principles calculations

Tight binding approach

Summary