Spin-orbit-induced exotic insulators in a three-orbital Hubbard model with (t2g)5 electrons
Spin-orbit-induced exotic insulators in a three-orbital Hubbard model with (t2g)5 electrons
复制标题
具有 (t2g)5 电子的三轨道哈伯德模型中的自旋轨道诱导的奇异绝缘体
DOI：
10.1103/physrevb.91.125122
复制
发表时间：
2015
影响因子：
3.7
通讯作者：
and S. Yunoki
中科院分区：
文献类型：
--
作者：
T. Sato;T. Shirakawa;and S. Yunoki
在多轨道动力学平均场理论的基础上，研究了具有相对论自旋-轨道耦合（SOC）的三轨道Hubbard模型。数值计算采用基于强耦合展开的连续时间量子蒙特卡罗（CTQMC）方法。我们发现适当地选择碱基，即，的最大自旋轨道纠缠的基础上，大大改善了符号的问题，在CTQMC计算，这使我们能够处理完全洪德的耦合和对跳跃条款。这种改进对于在低温下达到SOC最显著影响电子结构的大SOC区域也是必不可少的。我们发现，金属-绝缘体的转变是由SOC引起的固定库仑相互作用。对于较小的库仑相互作用，绝缘态是反铁磁有序的，具有局部有效总角动量，其中基于（）的带基本上被半填充，而基于（）的带被完全占据。更有趣的是，对于较大的库仑相互作用，我们发现出现了激子绝缘态，其中电子-空穴对在基于（）和（）的能带中发生凝聚。激子绝缘体的起源以及实验意义进行了讨论。
On the basis of the multiorbital dynamical mean-field theory, a three-orbital Hubbard model with relativistic spin-orbit coupling (SOC) is studied at five electrons per site. The numerical calculations are performed by employing the continuous-time quantum Monte Carlo (CTQMC) method based on the strong-coupling expansion. We find that appropriately choosing bases, i.e., the maximally spin-orbit-entangled bases, drastically improves the sign problem in the CTQMC calculations, which enables us to treat exactly the full Hund's coupling and pair-hopping terms. This improvement is also essential to reach at low temperatures for a large SOC region where the SOC most significantly affects the electronic structure. We show that a metal-insulator transition is induced by the SOC for fixed Coulomb interactions. The insulating state for smaller Coulomb interactions is antiferromagnetically ordered with the local effective total angular momentum, in which the ()-based band is essentially half filled, while the ()-based bands are completely occupied. More interestingly, for larger Coulomb interactions, we find that an excitonic insulating state emerges, where the condensation of an electron-hole pair in the ()- and ()-based bands occurs. The origin of the excitonic insulator as well as the experimental implication is discussed.