Band topology and related spin (or pseudo-spin) physics of photons provide us with a new dimension for manipulating light, which is potentially useful for information communication and data storage. Especially, the quantum spin Hall effect of light, where electromagnetic waves propagate along surfaces of samples with strong spin-momentum locking, paves the way for achieving topologically protected photonic spin transport. Recently, the conventional bulk-edge correspondence of the band topology has been extended to higher-order cases that enables the explorations of topological states with codimensions larger than 1 such as hinge and corner states. Here, for the first time, we demonstrate a higherorder quantum spin Hall effect of light by utilizing an all-dielectric C6v-symmetric photonic crystal. We observe corner states with opposite pseudospin polarizations at different corners owing to nontrivial higher-order topology and finite spin-spin coupling. By applying the spin-polarized excitation sources, we can selectively excite the corner states at different spatial positions through spin-momentum-locked decaying edge states, resembling the quantum spin Hall effect in a higher-order manner. Our work which breaks the barriers between the spin photonics and higher-order topology opens the frontiers for studying lower-dimensional spinful classical surface waves and supports explorations in robust communications.
Higher odd-order nonlinear Hall effect in magnetic topological insulator Mn(Bi1-xSbx)2Te4
National Laboratory of Solid State Microstructures, Collaborative Innovation Center of Advanced Microstructures, Jiangsu Physical Science Research Center, and School of Physics, Nanjing University（南京大学固体微观结构国家重点实验室、先进微结构协同创新中心、江苏省物理科学研究中心组和物理学院）；Institute of Atom Manufacturing, Nanjing University（南京大学原子制造研究所）；Nanjing Institute of Atomic Scale Manufacturing（南京原子尺度制造研究所）；School of Materials Science and Intelligent Engineering, Nanjing University（南京大学材料科学与智能工程学院）；Jiangsu Provincial Key Laboratory of Advanced Photonic and Electronic Materials, State Key Laboratory of Spintronics Devices and Technologies, School of Electronic Science and Engineering, Nanjing University（南京大学电子科学与工程学院、江苏省先进光子与电子材料重点实验室、自旋电子学器件与技术国家重点实验室）；Center for Quantum Transport and Thermal Energy Science, Institute of Physics Frontiers and Interdisciplinary Sciences, School of Physics and Technology, Nanjing Normal University（南京师范大学物理科学与技术学院、前沿交叉科学研究院、量子输运与热能科学中心）；Suzhou Laboratory（苏州实验室）
Discovery of Higher-Order Topological Insulators using the Spin Hall Conductivity as a Topology Signature
拓扑绝缘体是一种当$d$维绝缘体被限制在（$d-1$）维时具有金属边界态的物质相，它的发现和实现导致了几个潜在的应用。最近，它表明，受保护的拓扑状态可以表现在（$d-2$）维，如铰链和角状态的三维和二维系统，分别。这些非平凡的材料被称为高阶拓扑绝缘体（HOTI）。在这里，我们使用{ \it ab initio}计算和紧束缚模型的组合显示自旋霍尔效应和HOTI之间的连接。该模型演示了如何在HOTI相内出现非零的体中隙自旋霍尔电导率（SHC）。在此之后，我们进行了高通量密度泛函理论计算，以找到未知的HOTI，使用SHC作为标准。我们计算了693个绝缘体的SHC，得到7个稳定的二维HOTI。我们的工作指导新的实验和理论的进展高阶拓扑绝缘体的实现和应用。
Real-Space Approach to Light-Induced Hall Transport in Disordered Materials
Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC and BIST（加泰罗尼亚纳米科学与技术研究所（ICN2））；Department of Physics, Campus UAB（巴塞罗那自治大学物理系）；ICREA–Institució Catalana de Recerca i Estudis Avançats（加泰罗尼亚研究与高级研究学院）
