arXiv:1202.1610 · Physical Review B
Tuning into the Kitaev spin liquid phase: A spin model on the honeycomb lattice with two types of Heisenberg exchange couplings
Yue Yu, Long Liang, Qian Niu, Shaojing Qin
Abstract
We study a spin model on honeycomb lattice with two types of Heisenberg exchange couplings, $J$ and $\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{J}$, where $J$ is for the conventional spin and $\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{J}$ is for rotated spin. When $J=0$, the system is either in a stripy antiferromagnetic order ($\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{J}<0$, ferromagnetic for rotated spin) or a zigzag antiferromagnetic order ($\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{J}>0$, antiferromagnetic for rotated spin). The competition between two ferromagnetic orders or between two antiferromagnetic orders induces Kitaev's spin liquid phase, characterized by the exactly solvable Kitaev model ($J=\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{J}$). Our model can be applied to layered Mott insulators $A$${}_{2}$IrO${}_{3}$ ($A=\text{Li}$, Na). For a monolayer of Li${}_{2}$IrO${}_{3}$, we show that it is possible to tune the controlling parameter into the Kitaev spin liquid regime by a link-dependent Rashba spin-orbital coupling.