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.
@article{arxiv.0803.2927,
title = {Novel Jeff = 1/2 Mott State Induced by Relativistic Spin-Orbit Coupling in Sr2IrO4},
author = {B. J. Kim and Hosub Jin and S. J. Moon and J. -Y. Kim and B. -G. Park and C. S. Leem and Jaeju Yu and T. W. Noh and C. Kim and S. -J. Oh and J. -H. Park and V. Durairaj and G. Cao and E. Rotenberg},
journal= {arXiv preprint arXiv:0803.2927},
year = {2009}
}