Yin Zhong, Yu-Feng Wang, Yong-Qiang Wang, Hong-Gang Luo
By using an extended mean-field theory we study the phase diagram of the topological Kondo lattice model on the honeycomb lattice at half-filling, in which the conduction electrons are described by the Haldane model. Besides the well-defined Kondo insulator and normal antiferromagnetic spin-density-wave (N-SDW) state, it is found that a novel and nontrivial topological antiferromagnetic SDW state (T-SDW) with a quantized Hall conductance is possible if the quasiparticle gap is dominated by the next-nearest neighbor hopping rather than the antiferromagnetic order. By analyzing the low-energy effective Chern-Simon action and the corresponding chiral edge-state, the T-SDW could be considered as a quantum anomalous Hall insulator with antiferromagnetic long-range order. This novel state is apparently beyond Landau-Ginzburg paradigm, which can be attributed to the interplay of quantum anomalous Hall effect and the subtle antiferromagnetic order in the Kondo lattice-like model. While the transition between the SDW states and the Kondo insulator is found to be conventional (a first order transition), the transition between the N- and T-SDWs is, however, a topological quantum phase transition. It is expected that such a T-SDW state could be realized by experiments in ultra-cold atoms on the honeycomb optical lattice. The present work sheds light on the interplay between conduction electrons and the densely localized spins on the honeycomb lattice.
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http://arxiv.org/abs/1209.6411
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