Charge partitioning and anomalous hole doping in Rh-doped Sr2IrO4

TL;DR

This study investigates how Rh doping affects charge distribution in Sr2IrO4, revealing anomalous hole doping behavior that influences its electronic phases and implications for superconductivity research.

Contribution

It provides new insights into charge partitioning mechanisms in Rh-doped Sr2IrO4 using XANES, clarifying the doping process and its effects on electronic structure.

Findings

Charge transfer between Rh and Ir sites varies with doping level.

Holes are initially doped into the Jeff=1/2 band at low Rh concentrations.

Anomalous hole removal occurs at higher Rh doping levels.

Abstract

The simultaneous presence of sizable spin-orbit interactions and electron correlations in iridium oxides has led to predictions of novel ground states including Dirac semimetals, Kitaev spin liquids, and superconductivity. Electron and hole doping studies of spin-orbit assisted Mott insulator Sr2IrO4 are being intensively pursued due to extensive parallels with the La2CuO4 parent compound of Cuprate superconductors. In particular, the mechanism of charge doping associated with replacement of Ir with Rh ions remains controversial with profound consequences for the interpretation of electronic structure and transport data. Using x-ray absorption near edge structure (XANES) measurements at the Rh L, K- and Ir L- edges we observe anomalous evolution of charge partitioning between Rh and Ir with Rh doping. The partitioning of charge between Rh and Ir sites progresses in a way that holes are initially doped into the Jeff=1/2 band at low x only to be removed from it at higher x values. This anomalous hole doping naturally explains the re-entrant insulating phase in the phase diagram of Rh doped Sr2IrO4 and ought to be considered when searching for superconductivity and other emergent phenomena in iridates doped with 4d elements