Computational Condensed Matter Physics Laboratory, RIKEN ASI, Wako, Saitama 351-0198, Japan.
Phys Rev Lett. 2010 Nov 19;105(21):216410. doi: 10.1103/PhysRevLett.105.216410.
Motivated by recent experiments of a novel 5d Mott insulator in Sr2IrO4, we have studied the two-dimensional three-orbital Hubbard model with a spin-orbit coupling λ. The variational Monte Carlo method is used to obtain the ground state phase diagram with varying an on-site Coulomb interaction U as well as λ. It is found that the transition from a paramagnetic metal to an antiferromagnetic insulator occurs at a finite U=U(MI), which is greatly reduced by a large λ, characteristic of 5d electrons, and leads to the "spin-orbit-induced" Mott insulator. It is also found that the Hund's coupling induces the anisotropic spin exchange and stabilizes the in-plane antiferromagnetic order. We have further studied the one-particle excitations by using the variational cluster approximation and revealed the internal electronic structure of this novel Mott insulator. These findings are in agreement with experimental observations on Sr2IrO4.
受 Sr2IrO4 中新型 5d 莫特绝缘体实验的启发，我们研究了具有自旋轨道耦合 λ 的二维三轨道 Hubbard 模型。使用变分蒙特卡罗方法获得了随局域库仑相互作用 U 以及 λ 变化的基态相图。结果发现，从顺磁金属到反铁磁绝缘体的转变发生在有限的 U=U(MI)处，这一转变由于较大的 λ（5d 电子的特征）大大减小，导致了“自旋轨道诱导”莫特绝缘体。还发现，Hund 耦合诱导各向异性自旋交换并稳定面内反铁磁序。我们进一步通过变分团近似研究了单粒子激发，并揭示了这种新型莫特绝缘体的内部电子结构。这些发现与 Sr2IrO4 的实验观测结果一致。
