“かごめ(Kagome)金属”:物理学家发现了新的量子电子材料 诸平 据美国麻省理工学院( Massachusetts Institute of Technology , MIT)2018年3月19日提供的信息,该大学的物理学家已经发现了新的量子电子材料。 (Left to right) Joe Checkelsky, Linda Ye, Min Gu Kang, and Riccardo Comin. Credit: Takehito Suzuki 如果一种金属或其他导电材料可以在原子尺度上像日本篮球的网篮一样,编织成高度对称的交错的三角形,材料的性质将会怎样呢?日本将这样的图案称之为笼目( kagome ),日语发音为かごめ。单个原子排列成类似かごめ( kagome )的三角形图案,从理论上讲它应该具有奇异的电子特性。 来自美国麻省理工学院的物理学家与美国哈佛大学( Harvard University ) 和劳伦斯·伯克利国家实验室( Lawrence Berkeley National Laboratory )的科学家合作,已经制备出类似于かごめ ( kagome ) 图案的新材料。相关研究结果已于 2018 年 3 月 19 日在《自然》( Nature )杂志网站上发表 ——Linda Ye, Mingu Kang, Junwei Liu, Felix von Cube, Christina R. Wicker, Takehito Suzuki, Chris Jozwiak, Aaron Bostwick, Eli Rotenberg, David C. Bell, Liang Fu, Riccardo Comin, Joseph G. Checkelsky. Massive Dirac fermions in a ferromagnetic kagome metal . Nature, 2018. nature.com/articles/doi:10.1038/nature25987 。 Massive Dirac fermions in a ferromagnetic kagome metal.pdf 研究者在文章中声称,他们首次产生了笼目型导电金属晶体,而且是由铁和锡原子层构成,每个原子层都是以笼目晶格(kagome lattice)形式重复安排。当晶体内的 かごめ( kagome ) 层上有电流通过时,研究人员观察到原子的三角排列在传递电流中产生了奇怪的、量子般的行为。电子不是直接穿过晶格,而是在晶格中转向或者弯曲迂回。这种行为就是所谓的量子霍尔效应(quantum Hall effect)的三维版本,在这种效应中,通过二维物质的电子会呈现出一种“手性的、拓扑的状态”,在这种状态下,电子会弯曲成紧密的、圆形的路径,并沿着边缘流动而不会失去能量。 麻省理工学院的物理学助理教授Joseph Checkelsky说:“通过构建具有内在磁性的铁的 かごめ( kagome ) 网络,这种奇异的行为会持续到室温和更高的温度。” “晶体中的电荷不仅能感知来自这些原子的磁场,而且还能从晶格中得到纯量子力学的磁力。这可能导致在未来几代材料中,类似超导的完美传导。”更多信息请注意浏览原文或者相关其他报道。 Abstract The kagome lattice is a two-dimensional network of corner-sharing triangles 1 that is known to host exotic quantum magnetic states 2 , 3 , 4 . Theoretical work has predicted that kagome lattices may also host Dirac electronic states 5 that could lead to topological 6 and Chern 7 insulating phases, but these states have so far not been detected in experiments. Here we study the d -electron kagome metal Fe 3 Sn 2 , which is designed to support bulk massive Dirac fermions in the presence of ferromagnetic order. We observe a temperature-independent intrinsic anomalous Hall conductivity that persists above room temperature, which is suggestive of prominent Berry curvature from the time-reversal-symmetry-breaking electronic bands of the kagome plane. Using angle-resolved photoemission spectroscopy, we observe a pair of quasi-two-dimensional Dirac cones near the Fermi level with a mass gap of 30 millielectronvolts, which correspond to massive Dirac fermions that generate Berry-curvature-induced Hall conductivity. We show that this behaviour is a consequence of the underlying symmetry properties of the bilayer kagome lattice in the ferromagnetic state and the atomic spin–orbit coupling. This work provides evidence for a ferromagnetic kagome metal and an example of emergent topological electronic properties in a correlated electron system. Our results provide insight into the recent discoveries of exotic electronic behaviour in kagome-lattice antiferromagnets 8 , 9 , 10 and may enable lattice-model realizations of fractional topological quantum states 11 , 12 .