School of Physics and Astronomy, University of Birmingham, Birmingham B15 2TT, UK.
International Collaborative Laboratory of 2D Materials for Optoelectronic Science and Technology of Ministry of Education, Shenzhen University, Shenzhen 518060, China.
Science. 2018 Mar 2;359(6379):1013-1016. doi: 10.1126/science.aaq1221. Epub 2018 Jan 11.
Weyl points are the crossings of linearly dispersing energy bands of three-dimensional crystals, providing the opportunity to explore a variety of intriguing phenomena such as topologically protected surface states and chiral anomalies. However, the lack of an ideal Weyl system in which the Weyl points all exist at the same energy and are separated from any other bands poses a serious limitation to the further development of Weyl physics and potential applications. By experimentally characterizing a microwave photonic crystal of saddle-shaped metallic coils, we observed ideal Weyl points that are related to each other through symmetry operations. Topological surface states exhibiting helicoidal structure have also been demonstrated. Our system provides a photonic platform for exploring ideal Weyl systems and developing possible topological devices.
外尔点是三维晶体中线性色散能带的交点，为探索各种有趣的现象提供了机会，如拓扑保护的表面态和手征反常。然而，缺乏一个理想的外尔体系，其中所有的外尔点都处于相同的能量且与任何其他能带分离，这对外尔物理和潜在应用的进一步发展构成了严重的限制。通过实验表征具有鞍形金属线圈的微波光子晶体，我们观察到了通过对称操作相关的理想外尔点。还证明了具有螺旋结构的拓扑表面态。我们的系统为探索理想的外尔体系和开发可能的拓扑器件提供了一个光子平台。
