Topological cavity states in two-dimensional photonic/phononic chips
Jian-Hua Jiang, School of Physical Science and Technology, Soochow University
Topological insulators are electronic systems with an insulating bulk and topologically protected boundary states. Conventional 2D topological insulators induce 1D edge states. Recent studies indicate that lower-dimensional topological states are also possible in electronic systems, which, however, has been confirmed only in Bismuth in experiments . In this talk, I will show that lower-dimensional topological wave trapping can be achieved in photonic and acoustic systems through several different mechanisms. First, with concurrent real-space and wavevector-space topology, we show topological 0D light-trapping on a dislocation . Second, with two different schemes of higher-order topological insulators, we demonstrate topological 0D corner states in photonic crystals and sonic crystals [3,4]. Finally, we show that a novel topological state, named as hierarchical topological multipole insulators, which exhibits both topological dipole and quadrupole orders in a single system, can be realized in macroscopic sonic crystals . The underlying physics indicates the possibility of achieving frequency-stable topological cavity states in two-dimensional photonic/phononic chips that may enable scalable quantum photonic interface and other unprecedented functions in integrated photonics/acoustics.
 F. Schindler et al. Higher-order topology in bismuth. Nature Physics 14, 918-924 (2018).
 Fei-Fei Li, Hai-Xiao Wang, Zhan Xiong, Qun Lou, Ping Chen, Rui-Xin Wu, Yin Poo, Jian-Hua Jiang, and Sajeev John. Topological light-trapping on a dislocation. Nature Communications 9, 2462 (2018)
 Bi Ye Xie, Hong Fei Wang, Hai-Xiao Wang, Xue Yi Zhu, Jian-Hua Jiang, Ming Hui Lu, and Yan Feng Chen. Second-order photonic topological insulator with corner states. arXiv:1805.07555. Physical Review Letters under review.
 Xiujuan Zhang, Hai-Xiao Wang, Zhi-Kang Lin, Yuan Tian, Biye Xie, Ming-Hui Lu, Yan-Feng Chen, and Jian-Hua Jiang. Observation of second-order topological insulators in sonic crystals. arXiv:1806.10028. Nature Physics under review.
 Zhi-Kang Lin, Xiujuan Zhang, Hai-Xiao Wang, Yuan Tian, Ming-Hui Lu, Yan-Feng Chen, and Jian-Hua Jiang. Discovery of hierarchical topological multipole insulators. Submitted to Nature Materials.