Unconventional magnetic field response of the hyperhoneycomb Kitaev magnet $\beta -{\text{Li}}_2{\text{IrO}}_3$

Abstract

We present a unified description of the response of the hyperhoneycomb Kitaev magnet $\beta$-${\text{Li}}_2{\text{IrO}}_3$ to applied magnetic fields along the orthorhombic directions $\mathbf{a}$, $\mathbf{b}$ and $\mathbf{c}$. This description is based on the minimal nearest-neighbor $J$-$K$-$\Gamma$ model and builds on the idea that the incommensurate counter-rotating order observed experimentally at zero field can be treated as a long-distance twisting of a nearby commensurate order with six spin sublattices. The results reveal that the behavior of the system for $\mathbf{H}\parallel \mathbf{a}$, $\mathbf{H}\parallel \mathbf{b}$ and $\mathbf{H}\parallel \mathbf{c}$ share a number of qualitative features, including: i) a strong intertwining of the modulated, counter-rotating order with a set of uniform orders; ii) the disappearance of the modulated order at a critical field $H^{\ast }$, whose value is strongly anisotropic with $H_{\mathbf{b}}^{\ast }<H_{\mathbf{c}}^{\ast }\ll H_{\mathbf{a}}^{\ast }$; iii) the presence of a robust zigzag phase above $H^{\ast }$; and iv) the fulfillment of the Bragg peak intensity sum rule. It is noteworthy that the disappearance of the modulated order for $\mathbf{H}\parallel \mathbf{c}$ proceeds via a `metamagnetic' first-order transition which does not restore all broken symmetries. This implies the existence of a second finite-$T$ phase transition at higher magnetic fields. We also demonstrate that quantum fluctuations give rise to a significant reduction of the local moments for all directions of the field. The results for the total magnetization for $\mathbf{H}\parallel \mathbf{b}$ are consistent with available data and confirm a previous assertion that the system is very close to the highly-frustrated $K$-$\Gamma$ line in parameter space. Our predictions for the magnetic response for fields along $\mathbf{a}$ and $\mathbf{c}$ await experimental verification.

19 pages, 12 figures

References in corpus (15)

• Mott Insulators in the Strong Spin-Orbit Coupling Limit: From Heisenberg to a Quantum Compass and Kitaev Models
• $\alpha$-RuCl3: a Spin-Orbit Assisted Mott Insulator on a Honeycomb Lattice
• Models and Materials for Generalized Kitaev Magnetism
• Magnetic order in $\alpha$-RuCl${}_3$: a honeycomb lattice quantum magnet with strong spin-orbit coupling
• Hyper-honeycomb iridate $\beta$-Li2IrO3 as a platform for Kitaev magnetism
• Long range magnetic ordering in Na${}_2$IrO${}_3$
• Anisotropic Ru3+ 4d5 magnetism in the alpha-RuCl3 honeycomb system: susceptibility, specific heat and Zero field NMR
• Magnetization processes of zigzag states on the honeycomb lattice: Identifying spin models for $\alpha$-RuCl${}_3$ and Na${}_2$IrO${}_3$
• Non-coplanar and counter-rotating incommensurate magnetic order stabilized by Kitaev interactions in $\gamma$-Li2IrO3
• Unconventional magnetic order on the hyperhoneycomb Kitaev lattice in $\beta$-Li2IrO3: full solution via magnetic resonant x-ray diffraction
• Honeycomb-lattice Heisenberg-Kitaev model in a magnetic field: Spin canting, metamagnetism, and vortex crystals
• Theory of Magnetic Phase Diagrams in Hyperhoneycomb and Harmonic-honeycomb Iridates
• Revealing frustrated local moment model for pressurized hyperhoneycomb iridate: paving a way toward quantum spin liquid
• Chiral magnetism and helimagnons in a pyrochlore antiferromagnet
• Helimagnons in a chiral ground state of the pyrochlore antiferromagnets

Cited by in corpus (2)

• Ground-State Phase Diagram of the Kitaev-Heisenberg Model on a Three-dimensional Hyperhoneycomb Lattice
• Non-Loudon-Fleury Raman scattering in spin-orbit coupled Mott insulators