Symmetric spin-orbital-Hubbard model on honeycomb lattice: An origin of Kitaev model
Yue Yu
Abstract
We present a single band Hubbard model on honeycomb lattice with link-symmetric spin-orbital interaction. In the large $U$ limit, this model is mapped to a conventional antiferromangentic (AFM) Heisenberg model combining with a 'zig-zag' AFM Heisenberg one. The latter AFM order was favored by recent experiments for A$_2$IrO$_3$ (A=Na, Li) [4-6]. Competition between two different AFM orders leads to a spin liquid phase characterized by Kitaev model that happens if the spin-orbital coupling has the same strength as the hopping amplitude. This deepens our understanding of the origin of the Kitaev coupling: It comes from the balance between the hopping and spin-orbital couplings but to get rid of the hopping. In a moderate $U$, this model has a charge-spin gapped phase with two different spinon excitations. In a weak interaction, the original gapless Dirac fermion is gapped by the spin-orbital coupling while a new gapless Dirac fermion appears at the same Dirac points.
 
 
Time: Mar. 14th, 2012 (Wednesday) 16:00
Place: IOP D-210 Conference Room
Contact: Ying Deng 82649414