Ren Yafei, Jiang Hong-Chen, Qiao Zhenhua, Sheng D N
ICQD, Hefei National Laboratory for Physical Sciences at Microscale, CAS Key Laboratory of Strongly-Coupled Quantum Matter Physics, and Department of Physics, University of Science and Technology of China, Hefei, Anhui 230026, China.
Department of Physics and Astronomy, California State University, Northridge, California 91330, USA.
Phys Rev Lett. 2021 Mar 19;126(11):117602. doi: 10.1103/PhysRevLett.126.117602.
We study the quantum phase diagram of electrons on kagome lattice with half-filled lowest flat bands by considering the antiferromagnetic Heisenberg interaction J, and short-range Coulomb interaction V. In the weak J regime, we identify a fully spin-polarized phase. The presence of finite V drives a spontaneous chiral current, which makes the system an orbital Chern insulator by contributing an orbital magnetization. Such an out-of-plane orbital magnetization allows the presence of a Chern insulating phase independent of the spin orientation in contrast to the spin-orbit coupling induced Chern insulator that disappears with in-plane ferromagnetism constrained by symmetry. Such a symmetry difference provides a criterion to distinguish the physical origin of topological responses in kagome systems. The orbital Chern insulator is robust against small coupling J. By further increasing J, we find that the ferromagnetic topological phase is suppressed, which first becomes partially polarized and then enters a nonmagnetic phase with spin and charge nematicity. The frustrated flat band allows the spin and Coulomb interaction to play an essential role in determining the quantum phases.
我们通过考虑反铁磁海森堡相互作用J和短程库仑相互作用V，研究了具有半填充最低平带的 kagome 晶格上电子的量子相图。在弱J regime中，我们确定了一个完全自旋极化相。有限V的存在驱动了自发手征电流，通过贡献轨道磁化强度，使系统成为轨道陈绝缘体。与由对称性限制的面内铁磁性导致消失的自旋轨道耦合诱导陈绝缘体不同，这种面外轨道磁化强度允许存在与自旋取向无关的陈绝缘相。这种对称性差异提供了一个区分 kagome 系统中拓扑响应物理起源的标准。轨道陈绝缘体对小耦合J具有鲁棒性。通过进一步增加J，我们发现铁磁拓扑相受到抑制，首先变为部分极化，然后进入具有自旋和电荷向列性的非磁相。受挫的平带使得自旋和库仑相互作用在确定量子相方面发挥重要作用。
