https://doi.org/10.1140/epjb/e2013-31091-7
Regular Article
Half-filled Kondo lattice on the honeycomb lattice
1
Center for Interdisciplinary Studies Key Laboratory for Magnetism
and Magnetic Materials of the MoE, Lanzhou University, Lanzhou
730000, P.R.
China
2
Institute of Theoretical Physics, Lanzhou University,
Lanzhou
730000, P.R.
China
3
Beijing Computational Science Research Center,
Beijing
100084, P.R.
China
a
e-mail: zhongy05@hotmail.com
Received: 5 December 2012
Received in final form: 27 February 2013
Published online: 29 April 2013
The unique linear density of state around the Dirac points for the honeycomb lattice brings much novel features in strongly correlated models. Here we study the ground-state phase diagram of the Kondo lattice model on the honeycomb lattice at half-filling by using an extended mean-field theory. By treating magnetic interaction and Kondo screening on an equal footing, it is found that besides a trivial discontinuous first-order quantum phase transition between well-defined Kondo insulator and antiferromagnetic insulating state, there can exist a wide coexistence region with both Kondo screening and antiferromagnetic orders in the intermediate coupling regime. In addition, the stability of Kondo insulator requires a minimum strength of the Kondo coupling. These features are attributed to the linear density of state, which are absent in the square lattice. Furthermore, fluctuation effect beyond the mean-field decoupling is analyzed and the corresponding antiferromagnetic spin-density-wave transition falls into the O(3) universal class. Comparatively, we also discuss the Kondo necklace and the Kane-Mele-Kondo (KMK) lattice models on the same lattice. Interestingly, it is found that the topological insulating state is unstable to the usual antiferromagnetic ordered states at half-filling for the KMK model. The present work may be helpful for further study on the interplay between conduction electrons and the densely localized spins on the honeycomb lattice.
Key words: Solid State and Materials
© EDP Sciences, Società Italiana di Fisica and Springer-Verlag, 2013
