PMID- 32441985 OWN - NLM STAT- PubMed-not-MEDLINE LR - 20200525 IS - 1079-7114 (Electronic) IS - 0031-9007 (Linking) VI - 124 IP - 18 DP - 2020 May 8 TI - Direct Observation of Flatband Loop States Arising from Nontrivial Real-Space Topology. PG - 183901 LID - 10.1103/PhysRevLett.124.183901 [doi] AB - Topological properties of lattices are typically revealed in momentum space using concepts such as the Chern number. Here, we study unconventional loop states, namely, the noncontractible loop states (NLSs) and robust boundary modes, mediated by nontrivial topology in real space. While such states play a key role in understanding fundamental physics of flatband systems, their experimental observation has been hampered because of the challenge in realizing desired boundary conditions. Using a laser-writing technique, we optically establish photonic kagome lattices with both an open boundary by properly truncating the lattice, and a periodic boundary by shaping the lattice into a Corbino geometry. We thereby demonstrate the robust boundary modes winding around the entire edge of the open lattice and, more directly, the NLSs winding in a closed loop akin to that in a torus. We prove that the NLSs due to real-space topology persist in ideal Corbino-shaped kagome lattices of arbitrary size. Our results could be of great importance for our understanding of the singular flatbands and the intriguing physics phenomenon applicable for strongly interacting systems. FAU - Ma, Jina AU - Ma J AD - The MOE Key Laboratory of Weak-Light Nonlinear Photonics, TEDA Applied Physics Institute and School of Physics, Nankai University, Tianjin 300457, China. FAU - Rhim, Jun-Won AU - Rhim JW AD - Department of Physics and Astronomy, Seoul National University, Seoul 08826, Korea. AD - Center for Correlated Electron Systems, Institute for Basic Science (IBS), Seoul 08826, Korea. FAU - Tang, Liqin AU - Tang L AD - The MOE Key Laboratory of Weak-Light Nonlinear Photonics, TEDA Applied Physics Institute and School of Physics, Nankai University, Tianjin 300457, China. AD - Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan, Shanxi 030006, People's Republic of China. FAU - Xia, Shiqi AU - Xia S AD - The MOE Key Laboratory of Weak-Light Nonlinear Photonics, TEDA Applied Physics Institute and School of Physics, Nankai University, Tianjin 300457, China. FAU - Wang, Haiping AU - Wang H AD - The MOE Key Laboratory of Weak-Light Nonlinear Photonics, TEDA Applied Physics Institute and School of Physics, Nankai University, Tianjin 300457, China. FAU - Zheng, Xiuyan AU - Zheng X AD - The MOE Key Laboratory of Weak-Light Nonlinear Photonics, TEDA Applied Physics Institute and School of Physics, Nankai University, Tianjin 300457, China. FAU - Xia, Shiqiang AU - Xia S AD - The MOE Key Laboratory of Weak-Light Nonlinear Photonics, TEDA Applied Physics Institute and School of Physics, Nankai University, Tianjin 300457, China. AD - Engineering Lab for Optoelectronic Technology and Advanced Manufacturing, Henan Normal University, Xinxiang, 453007, China. FAU - Song, Daohong AU - Song D AD - The MOE Key Laboratory of Weak-Light Nonlinear Photonics, TEDA Applied Physics Institute and School of Physics, Nankai University, Tianjin 300457, China. AD - Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan, Shanxi 030006, People's Republic of China. FAU - Hu, Yi AU - Hu Y AD - The MOE Key Laboratory of Weak-Light Nonlinear Photonics, TEDA Applied Physics Institute and School of Physics, Nankai University, Tianjin 300457, China. AD - Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan, Shanxi 030006, People's Republic of China. FAU - Li, Yigang AU - Li Y AD - The MOE Key Laboratory of Weak-Light Nonlinear Photonics, TEDA Applied Physics Institute and School of Physics, Nankai University, Tianjin 300457, China. FAU - Yang, Bohm-Jung AU - Yang BJ AD - Department of Physics and Astronomy, Seoul National University, Seoul 08826, Korea. AD - Center for Correlated Electron Systems, Institute for Basic Science (IBS), Seoul 08826, Korea. AD - Center for Theoretical Physics (CTP), Seoul National University, Seoul 08826, Korea. FAU - Leykam, Daniel AU - Leykam D AD - Center for Theoretical Physics of Complex Systems, Institute for Basic Science, Daejeon 34126, Republic of Korea. FAU - Chen, Zhigang AU - Chen Z AD - The MOE Key Laboratory of Weak-Light Nonlinear Photonics, TEDA Applied Physics Institute and School of Physics, Nankai University, Tianjin 300457, China. AD - Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan, Shanxi 030006, People's Republic of China. AD - Department of Physics and Astronomy, San Francisco State University, San Francisco, California 94132, USA. LA - eng PT - Journal Article PL - United States TA - Phys Rev Lett JT - Physical review letters JID - 0401141 SB - IM EDAT- 2020/05/23 06:00 MHDA- 2020/05/23 06:01 CRDT- 2020/05/23 06:00 PHST- 2019/11/01 00:00 [received] PHST- 2020/04/16 00:00 [accepted] PHST- 2020/05/23 06:00 [entrez] PHST- 2020/05/23 06:00 [pubmed] PHST- 2020/05/23 06:01 [medline] AID - 10.1103/PhysRevLett.124.183901 [doi] PST - ppublish SO - Phys Rev Lett. 2020 May 8;124(18):183901. doi: 10.1103/PhysRevLett.124.183901.