Novel Jeff = 1/2 Mott State Induced by Relativistic Spin-Orbit Coupling in Sr2IrO4

TL;DR

This study reveals that in Sr2IrO4, strong spin-orbit coupling creates narrow Jeff=1/2 bands, leading to a Mott insulating state despite delocalized 5d electrons, indicating a new class of correlated-electron phenomena.

Contribution

It demonstrates the formation of a Jeff=1/2 Mott state driven by relativistic spin-orbit coupling in Sr2IrO4, combining experimental and theoretical approaches.

Findings

Jeff=1/2 bands are narrow despite delocalized electrons

Small correlation energy induces Mott insulating state

Relativistic spin-orbit coupling is crucial for electronic structure

Abstract

We investigated electronic structure of 5d transition-metal oxide Sr2IrO4 using angle-resolved photoemission, optical conductivity, and x-ray absorption measurements and first-principles band calculations. The system was found to be well described by novel effective total angular momentum Jeff states, in which relativistic spin-orbit (SO) coupling is fully taken into account under a large crystal field. Despite of delocalized Ir 5d states, the Jeff-states form so narrow bands that even a small correlation energy leads to the Jeff = 1/2 Mott ground state with unique electronic and magnetic behaviors, suggesting a new class of the Jeff quantum spin driven correlated-electron phenomena.