Covalent organic frameworks (COFs) are an emerging class of crystalline organic materials that have shown potential to be a new physical platform. In this work, a designed COF named AB-COF, which has novel enantiomorphic Kagome bands, is proposed and a feasible route to synthesize it is given. Via a combination of first-principles calculations and tight-binding analysis, we investigate the electronic structures and the phase interference of the COF. It becomes topologically nontrivial when doping one iodine atom in a unit cell. The Berry curvatures of the valence band (VB) and conduction band (CB) of the iodine-doped AB-COF show opposite values and different distributions. This provides an opportunity to study the new mechanism of circular dichroism from the different Berry curvatures of the VB and CB. Surprisingly, the circular-dichroism dissymmetry factor of AB-COF reaches a theoretical maximum value, and the oscillator strength data are in agreement with this result. When two iodine atoms are doped in a unit cell, the Berry curvatures of the VB and CB also have different values, but with more symmetry and similar distributions. This behavior enhances the circular dichroism with a wider range of dissymmetric absorption, and the circular dichroism dissymmetry factor also reaches its theoretical maximum value.

中文翻译：

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设计的共价有机框架中对映体 Kagome 带的拓扑和巨圆二色性


共价有机框架（COF）是一类新兴的结晶有机材料，已显示出成为新物理平台的潜力。在这项工作中，提出了一种名为AB-COF的设计COF，它具有新颖的对映体Kagome带，并给出了可行的合成路线。通过结合第一性原理计算和紧束缚分析，我们研究了 COF 的电子结构和相位干扰。当在晶胞中掺杂一个碘原子时，它在拓扑上变得不平凡。碘掺杂AB-COF的价带(VB)和导带(CB)的贝里曲率表现出相反的值和不同的分布。这为从VB和CB的不同贝里曲率研究圆二色性的新机制提供了机会。令人惊讶的是，AB-COF的圆二色性不对称因子达到了理论最大值，并且振荡器强度数据与该结果一致。当两个碘原子掺杂在一个晶胞中时，VB和CB的贝里曲率也有不同的值，但具有更多的对称性和相似的分布。这种行为增强了圆二色性，具有更宽的不对称吸收范围，圆二色性不对称因子也达到了理论最大值。