二维Kagome金属有机框架Eu$_2$(C$_6$H$_4$)$_3$中拓扑能隙的应变工程与可调陈数

中文摘要 AI 辅助

量子反常霍尔效应在没有外部磁场的情况下承载无耗散的手性边缘电流，但提高其工作温度和控制边缘通道的数量仍然困难。利用第一性原理计算，我们确定了二维金属有机Kagome铁磁体Eu$_2$(C$_6$H$_4$)$_3$是一种本征陈绝缘体，其拓扑能隙可以通过机械应变来扩大。该单层具有自旋轨道耦合诱导的72.7 meV能隙，在-8%双轴应变下拓宽至124.7 meV，实现了陈数$\mathcal{C}=-1$和单条手性边缘态的量子反常霍尔相。局域磁矩来自半填充的Eu $4f^{7}$壳层，而打开能隙的自旋轨道耦合由杂化进入碳Kagome带的Eu $5d$态承载。AB堆叠的双层铁磁耦合并累积每层陈数，给出$\mathcal{C}=-2$和两条共传播的手性通道。随后，垂直电场驱动双层经历$\mathcal{C}=-2$、$-3$和$-1$之间的一系列拓扑跃迁，切换边缘通道的数量。总之，应变、堆叠和门控在单一化学计量材料中提供了对能隙和陈数的三种不同调控手段。

英文摘要

The quantum anomalous Hall effect carries dissipationless chiral edge currents without an external magnetic field, yet raising its operating temperature and controlling the number of edge channels remain difficult. Using first-principles calculations, we identify the two-dimensional metal-organic kagome ferromagnet Eu$_2$(C$_6$H$_4$)$_3$ as an intrinsic Chern insulator whose topological gap can be enlarged by mechanical strain. The monolayer has a spin-orbit-coupling-induced gap of 72.7 meV that widens to 124.7 meV under -8% biaxial strain, realizing a quantum anomalous Hall phase with Chern number $\mathcal{C}=-1$ and a single chiral edge state. The local moments come from the half-filled Eu $4f^{7}$ shell, while the gap-opening spin-orbit coupling is carried by Eu $5d$ states hybridized into the carbon kagome bands. The AB-stacked bilayer couples ferromagnetically and accumulates the per-layer Chern numbers, giving $\mathcal{C}=-2$ with two co-propagating chiral channels. An out-of-plane electric field then drives the bilayer through a sequence of topological transitions among $\mathcal{C}=-2$, $-3$, and $-1$, switching the number of edge channels. Together, strain, stacking, and gating give three distinct handles on the gap and the Chern number within a single stoichiometric material.

发表机构

• Stanford University（斯坦福大学）

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