Magnetic Field Effect on Topological Spin Excitations in CrI3
Magnetic Field Effect on Topological Spin Excitations in CrI3
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DOI：
10.1103/physrevx.11.031047
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发表时间：
2021-08-31
影响因子：
12.5
通讯作者：
Dai, Pengcheng
中科院分区：
文献类型：
--
作者：
Chen, Lebing;Chung, Jae-Ho;Dai, Pengcheng
在最近发现的二维范德华(VDW)磁性材料中寻找拓扑自旋激发是非常重要的，因为它们在无耗散自旋电子学中具有潜在的应用。在二维VDW铁磁(FM)蜂窝晶格CrI3(TC=61K)中，声自旋波和光学自旋波在Dirac点处被间隙分开。这种能隙的存在是拓扑自旋激发的标志，如果它来自次最近邻(NNN)Dzyaloshinskii-Moriya(DM)或Cr蜂窝晶格内依赖键角的Kitaev相互作用。或者，该能隙被认为是由与拓扑自旋激发无关的电子关联效应引起的。在这里，我们使用非弹性中子散射来最终证明Kitaev相互作用和电子关联效应不能描述自旋波、狄拉克能隙和它们的面内磁场相关性。我们的结果支持DM相互作用是观测到的狄拉克能隙的微观起源的观点。此外，我们还发现沿c轴的近邻(NN)磁交换作用是反铁磁(AF)作用，而近邻(NN)作用是FM作用。因此，我们的结果揭示了观察到的CrI3薄层中c轴AF有序的起源，坚定地确定了块状CrI3中的微观自旋相互作用，并为2DVDW磁体中拓扑驱动的自旋激发提供了新的理解。
The search for topological spin excitations in recently discovered two-dimensional (2D) van der Waals (vdW) magnetic materials is important because of their potential applications in dissipationless spintronics. In the 2D vdW ferromagnetic (FM) honeycomb lattice CrI3 (TC = 61 K), acoustic and optical spin waves are found to be separated by a gap at the Dirac points. The presence of such a gap is a signature of topological spin excitations if it arises from the next-nearest-neighbor (NNN) Dzyaloshinskii-Moriya (DM) or bond-angle-dependent Kitaev interactions within the Cr honeycomb lattice. Alternatively, the gap is suggested to arise from an electron correlation effect not associated with topological spin excitations. Here, we use inelastic neutron scattering to conclusively demonstrate that the Kitaev interactions and electron correlation effects cannot describe spin waves, Dirac gaps, and their in-plane magnetic field dependence. Our results support the idea that the DM interactions are the microscopic origin of the observed Dirac gap. Moreover, we find that the nearest-neighbor (NN) magnetic exchange interactions along the c axis are antiferromagnetic (AF), and the NNN interactions are FM. Therefore, our results unveil the origin of the observed c-axis AF order in thin layers of CrI3, firmly determine the microscopic spin interactions in bulk CrI3, and provide a new understanding of topology-driven spin excitations in 2D vdW magnets.