Possible proximity of the Mott insulating Iridate Na2IrO3 to a topological phase: Phase diagram of the Heisenberg-Kitaev model in a magnetic field

Abstract

Motivated by the recent experimental observation of a Mott insulating state for the layered Iridate Na2IrO3, we discuss possible ordering states of the effective Iridium moments in the presence of strong spin-orbit coupling and a magnetic field. For a field pointing in the [111] direction - perpendicular to the hexagonal lattice formed by the Iridium moments - we find that a combination of Heisenberg and Kitaev exchange interactions gives rise to a rich phase diagram with both symmetry breaking magnetically ordered phases as well as a topologically ordered phase that is stable over a small range of coupling parameters. Our numerical simulations further indicate two exotic multicritical points at the boundaries between these ordered phases.

5 pages, 6 figures

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• Magnetization processes of zigzag states on the honeycomb lattice: Identifying spin models for $\alpha$-RuCl${}_3$ and Na${}_2$IrO${}_3$
• Honeycomb-lattice Heisenberg-Kitaev model in a magnetic field: Spin canting, metamagnetism, and vortex crystals
• Spin-orbit physics of j=1/2 Mott insulators on the triangular lattice
• Real-Space Parallel Density Matrix Renormalization Group
• A structural distortion induced magneto-elastic locking in Sr${}_2$IrO${}_4$ revealed through nonlinear optical harmonic generation
• Physical states and finite-size effects in Kitaev's honeycomb model: Bond disorder, spin excitations, and NMR lineshape
• Unified theory of spiral magnetism in the harmonic-honeycomb iridates α, β, γ Li2IrO3
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• Direct Evidence for the 'All-in/All-out' Magnetic Structure in the Pyrochlore Iridates from $\mu$SR
• Kitaev materials beyond iridates: order by quantum disorder and Weyl magnons in rare-earth double perovskites
• Theory of a quantum critical phenomenon in a topological insulator: (3+1)-dimensional quantum electrodynamics in solids
• Order-by-disorder and spin-orbital liquids in a distorted Heisenberg-Kitaev model
• Probing the stability of the spin liquid phases in the Kitaev-Heisenberg model using tensor network algorithms
• Effect of spin orbit coupling and Hubbard $U$ on the electronic structure of IrO${}_2$
• Entanglement Entropy and Spectra of the One-dimensional Kugel-Khomskii Model
• On the magnetic structure of Sr3Ir2O7: an x-ray resonant scattering study
• Crystalline Kitaev spin liquids
• Density-Matrix Renormalization Group Study of Extended Kitaev-Heisenberg Model
• High temperature thermodynamics of the honeycomb-lattice Kitaev-Heisenberg model: A high temperature series expansion study
• Investigation of unconventional reconstruction and electronic properties on the Na2IrO3 surface
• Strong-disorder renormalization for interacting non-Abelian anyon systems in two dimensions
• Thermal conductivity of local moment models with strong spin-orbit coupling
• Spin-orbit coupling in octamers in a spinel sulfide CuIr${}_2$S${}_4$: Competition between spin-singlet and quadrupolar states, and its relevance to remnant paramagnetism
• Electronic Structure and magnetism in Ir based double-perovskite Sr${}_2$CeIrO${}_6$