Abstract
We discuss the finite-temperature phase diagram of the Heisenberg-Kitaev model on the hexagonal lattice, which has been suggested to describe the spin-orbital exchange in the Mott-insulating iridate NaIrO. The model exhibits magnetically ordered ground states well beyond the isotropic Heisenberg limit as well as a gapless spin-liquid phase around the anisotropic Kitaev limit. Using a pseudofermion functional renormalization group (RG) approach we extract both the Curie-Weiss scale and the critical ordering scale from the RG flow of the magnetic susceptibility. The Curie-Weiss scale switches sign—indicating a transition of the dominant exchange from antiferromagnetic to ferromagnetic—deep in the magnetically ordered regime for which we find no significant frustration. We discuss our results in light of recent susceptibility measurements for NaIrO.
- Received 16 May 2011
DOI:https://doi.org/10.1103/PhysRevB.84.100406
©2011 American Physical Society