Constraints on the two-dimensional pseudospin- 12 Mott insulator description of Sr2IrO4

Abstract

${\mathrm{Sr}}_{2}{\mathrm{IrO}}_{4}$ has often been described via a simple, one-band pseudospin-$\frac{1}{2}$ model subject to electron-electron interactions on a square lattice, fostering analogies with cuprate superconductors believed to be well described by a similar model. In this work we argue---based on a detailed study of the low-energy electronic structure by circularly polarized spin and angle-resolved photoemission spectroscopy combined with dynamical mean-field theory calculations---that a pseudospin-$\frac{1}{2}$ model fails to capture the full complexity of the system. We show instead that a realistic multiband Hubbard Hamiltonian, accounting for the full correlated ${t}_{2g}$ manifold, provides a detailed description of the interplay between spin-orbital entanglement and electron-electron interactions and yields quantitative agreement with experiments. Our analysis establishes that the ${j}_{3/2}$ states make up a substantial percentage of the low-energy spectral weight, i.e., approximately 74% as determined from the integration of the $j$-resolved spectral function in the 0 to $\ensuremath{-}1.64\phantom{\rule{0.16em}{0ex}}\mathrm{eV}$ energy range. The results in our work are of relevance not only to Ir-based materials but also more generally to multiorbital materials with closely spaced energy scales.