High temperature thermodynamics of the honeycomb-lattice Kitaev-Heisenberg model: A high temperature series expansion study

Abstract

We develop high temperature series expansions for the thermodynamic properties of the honeycomb-lattice Kitaev-Heisenberg model. Numerical results for uniform susceptibility, heat capacity and entropy as a function of temperature for different values of the Kitaev coupling $K$ and Heisenberg exachange coupling $J$ (with $|J|\le |K|$) are presented. These expansions show good convergence down to a temperature of a fraction of $K$ and in some cases down to $T=K/10$. In the Kitaev exchange dominated regime, the inverse susceptibility has a nearly linear temperature dependence over a wide temperature range. However, we show that already at temperatures $10$-times the Curie-Weiss temperature, the effective Curie-Weiss constant estimated from the data can be off by a factor of 2. We find that the magnitude of the heat capacity maximum at the short-range order peak, is substantially smaller for small $J/K$ than for $J$ of order or larger than $K$. We suggest that this itself represents a simple marker for the relative importance of the Kitaev terms in these systems. Somewhat surprisingly, both heat capacity and susceptibility data on Na${}_2$IrO${}_3$ are consistent with a dominant {\it antiferromagnetic} Kitaev exchange constant of about $300-400$ $K$.

6 pages, 5 figures, series coefficients in supplementary materials

References in corpus (5)

• Mott Insulators in the Strong Spin-Orbit Coupling Limit: From Heisenberg to a Quantum Compass and Kitaev Models
• On the Origin of Zigzag Magnetic Order in Iridium Oxide Na2IrO3
• Possible proximity of the Mott insulating Iridate Na2IrO3 to a topological phase: Phase diagram of the Heisenberg-Kitaev model in a magnetic field
• Vaporization of Kitaev spin liquids
• Raman Scattering Signatures of Kitaev Spin Liquids in A${}_2$ IrO${}_3$ Iridates

Cited by in corpus (9)

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• Susceptibility anisotropy and its disorder evolution in models for Kitaev materials
• Thermodynamics of 3D Kitaev quantum spin liquids via tensor networks
• One- and two-magnon excitations in antiferromagnet PbFeBO4
• Ground-State Phase Diagram of the Kitaev-Heisenberg Model on a Three-dimensional Hyperhoneycomb Lattice
• Linked Cluster Expansions via Hypergraph Decompositions
• Longitudinal Magnetization and specific heat of the anisotropic Heisenberg antiferromagnet on Honeycomb lattice
• Thermodynamic behavior of modified integer-spin Kitaev models on the honeycomb lattice
• Susceptibility anisotropy and absence of ferroelectric order in the Kitaev spin liquid candidate Na${}_2$Co${}_2$TeO${}_6$