Topological systems containing near-field or far-field couplings between unit cells have been widely investigated in quantum and classic systems.Their band structures are well explained with theories based on tight-binding or multiple scattering formalism.However,characteristics of the topology of the bulk bands based on the joint modulation of near-field and far-field couplings are rarely studied.Such hybrid systems are hardly realized in real systems and cannot be described by neither tight-binding nor multiple scattering theories.Here,we pro-pose a hybrid-coupling photonic topological insulator based on a quasi-1D dimerized chain with the coexistence of near-field coupling within the unit cell and far-field coupling among all sites.Both theoretical and experimental results show that topological transition is realized by introducing near-field coupling for given far-field coupling conditions.In addition to closing and reopening the bandgap,the change in near-field coupling modulates the effective mass of photonics in the upper band from positive to negative,leading to an indirect bandgap,which cannot be achieved in conventional dimerized chains with either far-field or near-field coupling only.

CAIFU FAN;XI SHI;FENG WU;YUNHUI LI;HAITAO JIANG;YONG SUN;HONG CHEN

MOE Key Laboratory of Advanced Micro-Structured Materials,School of Physics Science and Engineering,Tongji University,Shanghai 200092,China;Department of Physics,Shanghai Normal University,Shanghai 200234,China;School of Optoelectronic Engineering,Guangdong Polytechnic Normal University,Guangzhou 510665,China

光子学研究（英文）

[1]CAIFU FAN;XI SHI;FENG WU;YUNHUI LI;HAITAO JIANG;YONG SUN;HONG CHEN-.Photonic topological transition in dimerized chains with the joint modulation of near-field and far-field couplings)[J].光子学研究（英文）,2022(01):41-49

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