Magnetic order and spin excitations in the Kitaev–Heisenberg model on a honeycomb lattice

Abstract

We consider the quasi-two-dimensional pseudo-spin-1/2 Kitaev–Heisenberg model proposed for A₂IrO₃ (A = Li, Na) compounds. The spin-wave excitation spectrum, the sublattice magnetization, and the transition temperatures are calculated in the random phase approximation for four different ordered phases observed in the parameter space of the model: antiferromagnetic, stripe, ferromagnetic, and zigzag phases. The Néel temperature and temperature dependence of the sublattice magnetization are compared with the experimental data on Na₂IrO₃.