Tuning into the Kitaev spin liquid phase: A spin model on the honeycomb lattice with two types of Heisenberg exchange couplings

We study a spin model on honeycomb lattice with two types of Heisenberg exchange couplings, J and (J) over tilde, where J is for the conventional spin and (J) over tilde is for rotated spin. When J = 0, the system is either in a stripy antiferromagnetic order ((J) over tilde < 0, ferromagnetic for rotated spin) or a zigzag antiferromagnetic order (<(J)over tilde> > 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 = (J) over tilde). Our model can be applied to layered Mott insulators A(2)IrO(3) (A = Li, Na). For a monolayer of Li2IrO3, 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. DOI: 10.1103/PhysRevB.87.041107