Topological antiferromagnetic spin-density-wave phase in an extended Kondo lattice model

TL;DR

This paper explores a topological antiferromagnetic spin-density-wave phase in an extended Kondo lattice model on a honeycomb lattice, revealing a novel quantum anomalous Hall insulator state with antiferromagnetic order and a topological quantum phase transition.

Contribution

The study introduces a topological antiferromagnetic SDW state in a Kondo lattice model, highlighting its quantum anomalous Hall characteristics and the nature of phase transitions involved.

Findings

Identification of a topological antiferromagnetic SDW state with quantized Hall conductance.

Discovery of a topological quantum phase transition between N- and T-SDWs.

Analysis of the transition as a Dirac fermion coupled to a Chern-Simons gauge field.

Abstract

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 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 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. Interestingly, such topological quantum phase transition can be described by Dirac fermions coupled to a U (1)Chern-Simon gauge field, which resembles the critical theory between bosonic integer quantum Hall phases and superfluid phase and also indicates that such a topological quantum phase transition may fall into the 3D-XY universal class. It is expected that the present work may shed light on the interplay between conduction electrons and the densely localized spins on the honeycomb lattice.