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Observation of Topological Flat Bands in the Kagome Semiconductor Nb3Cl8
Nano Letters ( IF 9.6 ) Pub Date : 2022-05-10 , DOI: 10.1021/acs.nanolett.2c00778 Zhenyu Sun 1, 2 , Hui Zhou 1, 2 , Cuixiang Wang 1, 2 , Shiv Kumar 3 , Daiyu Geng 1, 2 , Shaosheng Yue 1, 2 , Xin Han 1, 2 , Yuya Haraguchi 4 , Kenya Shimada 3 , Peng Cheng 1, 2 , Lan Chen 1, 2, 5 , Youguo Shi 1, 2, 5, 6 , Kehui Wu 1, 2, 5 , Sheng Meng 1, 2 , Baojie Feng 1, 2
Nano Letters ( IF 9.6 ) Pub Date : 2022-05-10 , DOI: 10.1021/acs.nanolett.2c00778 Zhenyu Sun 1, 2 , Hui Zhou 1, 2 , Cuixiang Wang 1, 2 , Shiv Kumar 3 , Daiyu Geng 1, 2 , Shaosheng Yue 1, 2 , Xin Han 1, 2 , Yuya Haraguchi 4 , Kenya Shimada 3 , Peng Cheng 1, 2 , Lan Chen 1, 2, 5 , Youguo Shi 1, 2, 5, 6 , Kehui Wu 1, 2, 5 , Sheng Meng 1, 2 , Baojie Feng 1, 2
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The destructive interference of wavefunctions in a kagome lattice can give rise to topological flat bands (TFBs) with a highly degenerate state of electrons. Recently, TFBs have been observed in several kagome metals, including Fe3Sn2, FeSn, CoSn, and YMn6Sn6. Nonetheless, kagome materials that are both exfoliable and semiconducting are lacking, which seriously hinders their device applications. Herein, we show that Nb3Cl8, which hosts a breathing kagome lattice, is gapped out because of the absence of inversion symmetry, while the TFBs survive because of the protection of the mirror reflection symmetry. By angle-resolved photoemission spectroscopy measurements and first-principles calculations, we directly observe the TFBs and a moderate band gap in Nb3Cl8. By mechanical exfoliation, we successfully obtain monolayer Nb3Cl8, which is stable under ambient conditions. In addition, our calculations show that monolayer Nb3Cl8 has a magnetic ground state, thus providing opportunities to study the interplay among geometry, topology, and magnetism.
中文翻译:
Kagome 半导体 Nb3Cl8 中拓扑平带的观察
Kagome 晶格中波函数的相消干涉可以产生具有高度简并态电子的拓扑平带 (TFB)。最近,已在几种kagome 金属中观察到TFB,包括Fe 3 Sn 2、FeSn、CoSn 和YMn 6 Sn 6。尽管如此,缺乏可剥离和半导体的kagome材料,这严重阻碍了它们的器件应用。在此,我们表明 Nb 3 Cl 8,它拥有一个呼吸的kagome晶格,由于缺乏反演对称性而被隔开,而TFB由于镜面反射对称性的保护而得以幸存。通过角分辨光电子能谱测量和第一性原理计算,我们直接观察到 TFB 和 Nb 3 Cl 8中的中等带隙。通过机械剥离,我们成功地获得了在环境条件下稳定的单层Nb 3 Cl 8 。此外,我们的计算表明单层 Nb 3 Cl 8具有磁性基态,从而为研究几何、拓扑和磁性之间的相互作用提供了机会。
更新日期:2022-05-10
中文翻译:
![](https://scdn.x-mol.com/jcss/images/paperTranslation.png)
Kagome 半导体 Nb3Cl8 中拓扑平带的观察
Kagome 晶格中波函数的相消干涉可以产生具有高度简并态电子的拓扑平带 (TFB)。最近,已在几种kagome 金属中观察到TFB,包括Fe 3 Sn 2、FeSn、CoSn 和YMn 6 Sn 6。尽管如此,缺乏可剥离和半导体的kagome材料,这严重阻碍了它们的器件应用。在此,我们表明 Nb 3 Cl 8,它拥有一个呼吸的kagome晶格,由于缺乏反演对称性而被隔开,而TFB由于镜面反射对称性的保护而得以幸存。通过角分辨光电子能谱测量和第一性原理计算,我们直接观察到 TFB 和 Nb 3 Cl 8中的中等带隙。通过机械剥离,我们成功地获得了在环境条件下稳定的单层Nb 3 Cl 8 。此外,我们的计算表明单层 Nb 3 Cl 8具有磁性基态,从而为研究几何、拓扑和磁性之间的相互作用提供了机会。