Origin of the different electronic structure of Rh- and Ru-doped Sr2IrO4

TL;DR

This study investigates how Ru and Rh doping differently alter the electronic structure of Sr2IrO4, revealing that Ru induces non-rigid band changes and inhomogeneous metallic states, unlike Rh, due to different hybridization effects.

Contribution

It provides a detailed ARPES analysis showing the contrasting effects of Ru and Rh doping on Sr2IrO4's electronic structure, emphasizing hybridization and inhomogeneity.

Findings

Ru doping causes non-rigid band shifts and inhomogeneous metallic states.

Rh doping can be approximated by a rigid band shift from the undoped case.

Hybridization with oxygen mediates the doping effects and differs between Ru and Rh.

Abstract

One way to induce insulator to metal transitions in the spin-orbit Mott insulator Sr2IrO4 is to substitute iridium with transition metals (Ru, Rh). However, this creates intriguing inhomogeneous metallic states, which cannot be described by a simple doping effect. We detail the electronic structure of the Ru-doped case with angle-resolved photoemission and show that, contrary to Rh, it cannot be connected to the undoped case by a rigid shift. We further identify bands below $E_F$ coexisting with the metallic ones that we assign to non-bonding Ir sites. We rationalize the differences between Rh and Ru by a different hybridization with oxygen, which mediates the coupling to Ir and sensitively affects the effective doping. We argue that the spin-orbit coupling does not control neither the charge transfer nor the transition threshold.