Microscopic study of spin-orbit-induced Mott insulator in Ir oxides

Abstract

Motivated by recent experiments of a novel 5$d$ Mott insulator in Sr${}_2$IrO${}_4$, we have studied the two-dimensional three-orbital Hubbard model with a spin-orbit coupling $\lambda$. The variational Monte Carlo method is used to obtain the ground state phase diagram with varying a on-site Coulomb interaction $U$ as well as $\lambda$. It is found that the transition from a paramagnetic metal to an antiferromagnetic (AF) insulator occurs at a finite $U=U_{\mathrm{MI}}$, which is greatly reduced by a large $\lambda$, characteristic of 5$d$ electrons, and leads to the "spin-orbit-induced" Mott insulator. It is also found that the Hund's coupling induces the anisotropic spin exchange and stabilizes the in-plane AF order. We have further studied the one-particle excitations using the variational cluster approximation, and revealed the internal electronic structure of this novel Mott insulator. These findings are in agreement with experimental observations on Sr${}_2$IrO${}_4$, and qualitatively different from those of extensively studied 3$d$ Mott insulators.

5 pages, 3 figures; accepted for publication in Phys. Rev. Lett

References in corpus (4)

• Mott Insulators in the Strong Spin-Orbit Coupling Limit: From Heisenberg to a Quantum Compass and Kitaev Models
• Novel Jeff = 1/2 Mott State Induced by Relativistic Spin-Orbit Coupling in Sr2IrO4
• Variational cluster approach to correlated electron systems in low dimensions
• Coulomb-Enhanced Spin-Orbit Splitting: The Missing Piece in the Sr2RhO4 Puzzle

Cited by in corpus (1)

• Twisted Hubbard Model for Sr2IrO4: Magnetism and Possible High Temperature Superconductivity