Valley Vortex States and Degeneracy Lifting via Photonic Higher-Band Excitation

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Title
Valley Vortex States and Degeneracy Lifting via Photonic Higher-Band Excitation
Author(s)
Daohong Song; Daniel Leykam; Jing Su; Xiuying Liu; Liqin Tang; Sheng Liu; Jianlin Zhao; Nikolaos K. Efremidis; Jingjun Xu; Zhigang Chen
Publication Date
2019-03
Journal
PHYSICAL REVIEW LETTERS, v.122, no.12, pp.123903 -
Publisher
AMER PHYSICAL SOC
Abstract
We demonstrate valley-dependent vortex generation in photonic graphene. Without breaking inversion symmetry, the excitation of two valleys leads to the formation of an optical vortex upon Bragg reflection to the third equivalent valley, with its chirality determined by the valley degree of freedom. Vortex-antivortex pairs with valley-dependent topological charge flipping are also observed and corroborated by numerical simulations. Furthermore, we develop a three-band effective Hamiltonian model to describe the dynamics of the coupled valleys and find that the commonly used two-band model is not sufficient to explain the observed vortex degeneracy lifting. Such valley-polarized vortex states arise from high-band excitation without a synthetic-field-induced gap opening. Our results from a photonic setting may provide insight for the study of valley contrasting and Berry-phase-mediated topological phenomena in other systems. © 2019 American Physical Society
URI
https://pr.ibs.re.kr/handle/8788114/6020
ISSN
0031-9007
Appears in Collections:
Center for Theoretical Physics of Complex Systems(복잡계 이론물리 연구단) > Journal Papers (저널논문)
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