Topological phases and edge modes of an uneven ladder  

作　　者：商文创 韩熠宁 Shimpei Endo 高超 Wen-Chuang Shang;Yi-Ning Han;Shimpei Endo;Chao Gao(Department of Physics,Zhejiang Normal University,Jinhua 321004,China;Key Laboratory of Optical Information Detection and Display Technology of Zhejiang,Zhejiang Normal University,Jinhua 321004,China;Department of Engineering Science,The University of Electro-Communications,Tokyo 182-8585,Japan)

机构地区：[1]Department of Physics,Zhejiang Normal University,Jinhua 321004,China [2]Key Laboratory of Optical Information Detection and Display Technology of Zhejiang,Zhejiang Normal University,Jinhua 321004,China [3]Department of Engineering Science,The University of Electro-Communications,Tokyo 182-8585,Japan

出　　处：《Chinese Physics B》2024年第8期154-168,共15页中国物理B（英文版）

基　　金：supported by the Natural Science Foundation of Zhejiang Province,China (Grant Nos.LR22A040001 and LY21A040004);the National Natural Science Foundation of China (Grant Nos.12074342 and 11835011)。

摘　　要：We investigate the topological properties of a two-chain quantum ladder with uneven legs,i.e.,the two chains differ in their periods by a factor of 2.Such an uneven ladder presents rich band structures classified by the closure of either direct or indirect bandgaps.It also provides opportunities to explore fundamental concepts concerning band topology and edge modes,including the difference of intracellular and intercellular Zak phases,and the role of the inversion symmetry(IS).We calculate the Zak phases of the two kinds and find excellent agreement with the dipole moment and extra charge accumulation.We also find that configurations with IS feature a pair of degenerate two-side edge modes emerging as the closure of the direct bandgap,while configurations without IS feature one-side edge modes emerging as not only the closure of both direct and indirect bandgaps but also within the band continuum.Furthermore,by projecting to the two sublattices,we find that the effective Bloch Hamiltonian corresponds to that of a generalized Su–Schrieffer–Heeger model or the Rice–Mele model whose hopping amplitudes depend on the quasimomentum.In this way,the topological phases can be efficiently extracted through winding numbers.We propose that uneven ladders can be realized by spin-dependent optical lattices and their rich topological characteristics can be examined by near future experiments.

关 键 词：ladder model symmetry-protected topological phase topological invariant bulk-boundary correspondence 

分 类 号：O469[理学—凝聚态物理]