title: Valley photonic crystals for control of spin and topology.
abstract: Photonic crystals offer unprecedented opportunity for light manipulation and applications in optical communication and sensing. Exploration of topology in photonic crystals and metamaterials with non-zero gauge field has inspired a number of intriguing optical phenomena such as one-way transport and Weyl points. Recently, a new degree of freedom, valley, has been demonstrated in two-dimensional materials. Here, we propose a concept of valley photonic crystals with electromagnetic duality symmetry but broken inversion symmetry. We observe photonic valley Hall effect originating from valley-dependent spin-split bulk bands, even in topologically trivial photonic crystals. Valley-spin locking behaviour results in selective net spin flow inside bulk valley photonic crystals. We also show the independent control of valley and topology in a single system that has been long pursued in electronic systems, resulting in topologically-protected flat edge states. Valley photonic crystals not only offer a route towards the observation of non-trivial states, but also open the way for device applications in integrated photonics and information processing using spin-dependent transportation.
authors.affiliation: State Key Laboratory of Optoelectronic Materials and Technologies &School of Physics, Sun Yat-Sen University, Guangzhou 510275, China.|NSF Nanoscale Science and Engineering Center (NSEC), University of California, Berkeley, California 94720, USA.
authors.forename: Jian-Wen
authors.identifier: 0000-0003-2379-554X
authors.initials: JW
authors.lastname: Dong
authors.affiliation: State Key Laboratory of Optoelectronic Materials and Technologies &School of Physics, Sun Yat-Sen University, Guangzhou 510275, China.
authors.forename: Xiao-Dong
authors.initials: XD
authors.lastname: Chen
authors.affiliation: NSF Nanoscale Science and Engineering Center (NSEC), University of California, Berkeley, California 94720, USA.
authors.forename: Hanyu
authors.initials: H
authors.lastname: Zhu
authors.affiliation: NSF Nanoscale Science and Engineering Center (NSEC), University of California, Berkeley, California 94720, USA.|Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA.
authors.forename: Yuan
authors.initials: Y
authors.lastname: Wang
authors.affiliation: NSF Nanoscale Science and Engineering Center (NSEC), University of California, Berkeley, California 94720, USA.|Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA.|Department of Physics, King Abdulaziz University, Jeddah 21589, Saudi Arabia.
authors.forename: Xiang
authors.initials: X
authors.lastname: Zhang