Honeycomb-lattice Gamma model in a magnetic field: hidden Néel order and spin-flop transition

Abstract

We show that a magnetic field in the high-symmetry direction lifts the macroscopic classical ground-state degeneracy of the honeycomb $\Gamma$ model and induces a long-range magnetic order. While a simple spin-polarized state is stabilized for the ferromagnetic $\Gamma$-exchange, a periodic $\sqrt{3}\times \sqrt{3}$ magnetic order is selected by magnetic field for the antiferromagnetic interaction. We show that the complex spin structure of the tripled unit cell can be described by the magnetization vector and a Néel order parameter, similar to those for the spin-flop state of a bipartite antiferromagnet. Indeed, the transition from the low-field plaquette-ordered spin liquid to the field-induced magnetic order can be viewed as a generalized spin-flop transition. An accidental O(2) degeneracy associated with rotation symmetry of the Néel vector is broken by either quantum or thermal fluctuations, leaving a six-fold degenerate ground state. At high fields, the breaking of the ground-state $Z_6$ symmetry is through two Berezinskii-Kosterlitz-Thouless transitions that enclose a critical XY phase.

arXiv comment6 pages, 5 figures

References in corpus (39)

• Anyons in an exactly solved model and beyond
• Mott Insulators in the Strong Spin-Orbit Coupling Limit: From Heisenberg to a Quantum Compass and Kitaev Models
• Kitaev-Heisenberg Model on Honeycomb Lattice: Possible Exotic Phases in Iridium Oxides $A_2$IrO${}_3$
• Mott physics and band topology in materials with strong spin-orbit interaction
• Generic spin model for the honeycomb iridates beyond the Kitaev limit
• On the Origin of Zigzag Magnetic Order in Iridium Oxide Na2IrO3
• Challenges in Design of Kitaev Materials: Magnetic Interactions from Competing Energy Scales
• Properties of a classical spin liquid: the Heisenberg pyrochlore antiferromagnet
• Low-temperature properties of classical, geometrically frustrated antiferromagnets
• Macroscopic magnetization jumps due to independent magnons in frustrated quantum spin lattices
• Half-magnetization plateau stabilized by structural distortion in the antiferromagnetic Heisenberg model on a pyrochlore lattice
• Vaporization of Kitaev spin liquids
• Magnetization processes of zigzag states on the honeycomb lattice: Identifying spin models for $\alpha$-RuCl${}_3$ and Na${}_2$IrO${}_3$
• Microscopic mechanism for higher-spin Kitaev model
• Cascade of magnetic-field-induced quantum phase transitions in a spin $1/2$ triangular-lattice antiferromagnet
• Orbital ordering and frustration of $p$-band Mott-insulators
• Importance of anisotropic exchange interactions in honeycomb iridates. Minimal model for zigzag antiferromagnetic order in Na${}_2$IrO${}_3$
• Octupolar ordering of classical kagome antiferromagnets in two and three dimensions
• Field induced transitions in a kagome antiferromagnet
• Dynamical and Topological Properties of the Kitaev Model in a [111] Magnetic Field
• Quantum stabilization of 1/3-magnetization plateau in Cs_2CuBr_4
• Field induced ordering in highly frustrated antiferromagnets
• Magnetic field induced quantum phases in a tensor network study of Kitaev magnets
• Orbital order in Mott insulators of spinless p-band fermions
• One Proximate Kitaev Spin Liquid in the $K$-$J$-$\Gamma$ Model on the Honeycomb Lattice
• Magnetic field induced intermediate quantum spin-liquid with a spinon Fermi surface
• Field-induced intermediate ordered phase and anisotropic interlayer interactions in $\alpha$-RuCl${}_3$
• Pseudo-Goldstone gaps and order-by-quantum-disorder in frustrated magnets
• Dirac and Chiral Quantum Spin Liquids on the Honeycomb Lattice in a Magnetic Field
• Dipolar order by disorder in the classical Heisenberg antiferromagnet on the kagome lattice
• Field-induced XY behavior in the S=1/2 antiferromagnet on the square lattice
• Classical and quantum spin dynamics of the honeycomb $\Gamma$ model
• Two-dimensional anisotropic Heisenberg antiferromagnet in a field
• Orbital ordering in e_g orbital systems: Ground states and thermodynamics of the 120 degree model
• Doubly degenerate orbital system in honeycomb lattice: implication of orbital state in layered iron oxide
• Plaquette order in classical spin liquid stabilized by strong off-diagonal exchange
• Magnetization plateaus and sublattice ordering in easy axis Kagome lattice antiferromagnets
• Orbital ice: an exact Coulomb phase on the diamond lattice
• Spin correlations in an isotropic spin-5/2 two-dimensional antiferromagnet