论文标题
过渡金属二分法元素双层中的轨道和山谷大厅效应
Disentangling orbital and valley Hall effects in bilayers of transition metal dichalcogenides
论文作者
论文摘要
最近已经显示，在2H结构相中，过渡金属二甲盐（TMD）的单层表现出相对较大的轨道霍尔电导率，其能量带隙内的旋转大厅的电导率消失了。但是，由于这些系统中的山谷大厅效应（VHE）也会产生轨道角动量的横向流动，因此在这些材料中区分两种效应在实验上变得具有挑战性。 VHE需要发生反转对称性破裂，发生在TMD单层中，而不是在双层中发生。我们表明，2H-mos $ _2 $的双层是轨道厅绝缘子，在没有旋转和山谷厅效果的情况下，它表现出很大的OHE。 This phase can be characterised by an orbital Chern number that assumes the value $\mathcal{C}_{L}=2$ for the 2H-MoS$_2$ bilayer and $\mathcal{C}_{L}=1$ for the monolayer, confirming the topological nature of these orbital-Hall insulator systems.我们的结果基于密度功能理论（DFT）和低能有效的模型计算，并强烈表明TMD的双层是高度合适的平台，可直接观察二维材料中轨道霍尔绝缘阶段。还讨论了我们对观察TMD双层中VHE的尝试的含义。
It has been recently shown that monolayers of transition metal dichalcogenides (TMDs) in the 2H structural phase exhibit relatively large orbital Hall conductivity plateaus within their energy band gaps, where their spin Hall conductivities vanish. However, since the valley Hall effect (VHE) in these systems also generates a transverse flow of orbital angular momentum it becomes experimentally challenging to distinguish between the two effects in these materials. The VHE requires inversion symmetry breaking to occur, which takes place in the TMD monolayers, but not in the bilayers. We show that a bilayer of 2H-MoS$_2$ is an orbital Hall insulator that exhibits a sizeable OHE in the absence of both spin and valley Hall effects. This phase can be characterised by an orbital Chern number that assumes the value $\mathcal{C}_{L}=2$ for the 2H-MoS$_2$ bilayer and $\mathcal{C}_{L}=1$ for the monolayer, confirming the topological nature of these orbital-Hall insulator systems. Our results are based on density functional theory (DFT) and low-energy effective model calculations and strongly suggest that bilayers of TMDs are highly suitable platforms for direct observation of the orbital Hall insulating phase in two-dimensional materials. Implications of our findings for attempts to observe the VHE in TMD bilayers are also discussed.
