Park Haedong, Gao Wenlong, Zhang Xiao, Oh Sang Soon
School of Physics and Astronomy, Cardiff University, Cardiff, CF24 3AA, UK.
Department of Physics, Paderborn University, Warburger Straße 100, Paderborn, 33 098, Germany.
Nanophotonics. 2022 Feb 2;11(11):2779-2801. doi: 10.1515/nanoph-2021-0692. eCollection 2022 Jun.
Topological insulators constitute one of the most intriguing phenomena in modern condensed matter theory. The unique and exotic properties of topological states of matter allow for unidirectional gapless electron transport and extremely accurate measurements of the Hall conductivity. Recently, new topological effects occurring at Dirac/Weyl points have been better understood and demonstrated using artificial materials such as photonic and phononic crystals, metamaterials and electrical circuits. In comparison, the topological properties of nodal lines, which are one-dimensional degeneracies in momentum space, remain less explored. Here, we explain the theoretical concept of topological nodal lines and review recent and ongoing progress using artificial materials. The review includes recent demonstrations of non-Abelian topological charges of nodal lines in momentum space and examples of nodal lines realized in photonic and other systems. Finally, we will address the challenges involved in both experimental demonstration and theoretical understanding of topological nodal lines.
拓扑绝缘体是现代凝聚态物质理论中最引人入胜的现象之一。物质拓扑态的独特且奇异的性质使得单向无隙电子输运以及霍尔电导率的极其精确测量成为可能。近来，利用诸如光子晶体、声子晶体、超材料和电路等人工材料，在狄拉克/外尔点处出现的新拓扑效应已得到更好的理解和展示。相比之下，作为动量空间中的一维简并的节线的拓扑性质仍较少被探索。在此，我们解释拓扑节线的理论概念，并回顾利用人工材料取得的近期及正在进行的进展。该综述包括近期在动量空间中节线的非阿贝尔拓扑电荷的展示以及在光子和其他系统中实现节线的例子。最后，我们将探讨在拓扑节线的实验展示和理论理解两方面所涉及的挑战。
