Feng Baojie, Fu Botao, Kasamatsu Shusuke, Ito Suguru, Cheng Peng, Liu Cheng-Cheng, Feng Ya, Wu Shilong, Mahatha Sanjoy K, Sheverdyaeva Polina, Moras Paolo, Arita Masashi, Sugino Osamu, Chiang Tai-Chang, Shimada Kenya, Miyamoto Koji, Okuda Taichi, Wu Kehui, Chen Lan, Yao Yugui, Matsuda Iwao
The Institute for Solid State Physics, The University of Tokyo, Kashiwa, Chiba, 277-8581, Japan.
Hiroshima Synchrotron Radiation Center, Hiroshima University, 2-313 Kagamiyama, Higashi-Hiroshima, 739-0046, Japan.
Nat Commun. 2017 Oct 18;8(1):1007. doi: 10.1038/s41467-017-01108-z.
Topological nodal line semimetals, a novel quantum state of materials, possess topologically nontrivial valence and conduction bands that touch at a line near the Fermi level. The exotic band structure can lead to various novel properties, such as long-range Coulomb interaction and flat Landau levels. Recently, topological nodal lines have been observed in several bulk materials, such as PtSn, ZrSiS, TlTaSe and PbTaSe. However, in two-dimensional materials, experimental research on nodal line fermions is still lacking. Here, we report the discovery of two-dimensional Dirac nodal line fermions in monolayer CuSi based on combined theoretical calculations and angle-resolved photoemission spectroscopy measurements. The Dirac nodal lines in CuSi form two concentric loops centred around the Γ point and are protected by mirror reflection symmetry. Our results establish CuSi as a platform to study the novel physical properties in two-dimensional Dirac materials and provide opportunities to realize high-speed low-dissipation devices.
拓扑节线半金属是一种新型的材料量子态，具有拓扑非平庸的价带和导带，它们在费米能级附近的一条线上相交。这种奇特的能带结构可导致各种新奇特性，如长程库仑相互作用和平坦的朗道能级。最近，在几种体材料中观察到了拓扑节线，如PtSn、ZrSiS、TlTaSe和PbTaSe。然而，在二维材料中，关于节线费米子的实验研究仍然缺乏。在此，我们基于理论计算和角分辨光电子能谱测量相结合的方法，报告了在单层CuSi中发现二维狄拉克节线费米子。CuSi中的狄拉克节线形成围绕Γ点的两个同心环，并由镜面对称性保护。我们的结果确立了CuSi作为研究二维狄拉克材料新奇物理特性的平台，并为实现高速低耗散器件提供了机会。
