Effects of non-Hermiticity on Su-Schrieffer-Heeger defect states

Lang, Li-Jun; Wang, You; Wang, Hailong; Chong, Yidong

doi:10.1103/physrevb.98.094307

Cited by 69 publications

(44 citation statements)

References 48 publications

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“…Biorthogonal [122] and non-Bloch bulk-boundary correspondences [123] are suggested. In contrast, non-Hermiticity does not inevitably destroy the bulk-boundary correspondence [77,78,[93][94][95][96][97], which is verified in a parity-time-symmetric non-Hermitian SSH model with staggered couplings and losses [85][86][87][88][89][90][91][92]. Questions arise: Why bulk-boundary correspondence fails in certain non-Hermitian systems?…”

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confidence: 96%

Bulk-boundary correspondence in a non-Hermitian system in one dimension with chiral inversion symmetry

2019

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Asymmetric coupling amplitudes effectively create an imaginary gauge field, which induces a non-Hermitian Aharonov-Bohm (AB) effect. Nonzero imaginary magnetic flux invalidates the bulk-boundary correspondence and leads to a topological phase transition. However, the way of non-Hermiticity appearance may alter the system topology. By alternatively introducing the non-Hermiticity under symmetry to prevent nonzero imaginary magnetic flux, the bulk-boundary correspondence recovers and every bulk state becomes extended; the bulk topology of Bloch Hamiltonian predicts the (non)existence of edge states and topological phase transition. These are elucidated in a non-Hermitian Su-Schrieffer-Heeger model, where chiral-inversion symmetry ensures the vanishing of imaginary magnetic flux. The average value of Pauli matrices under the eigenstate of chiralinversion symmetric Bloch Hamiltonian defines a vector field, the vorticity of topological defects in the vector field is a topological invariant. Our findings are applicable in other non-Hermitian systems. We first uncover the roles played by non-Hermitian AB effect and chiral-inversion symmetry for the breakdown and recovery of bulk-boundary correspondence, and develop new insights for understanding non-Hermitian topological phases of matter. arXiv:1809.03139v3 [cond-mat.mes-hall]

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confidence: 96%

Bulk-boundary correspondence in a non-Hermitian system in one dimension with chiral inversion symmetry

2019

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“…The nontrivial bulk topology in Hermitian systems can * wuyajie@xatu.edu.cn † Junpeng.Hou@utdallas.edu be detected by defects, such as edges, π-flux, dislocations and vortices [48][49][50][51][52][53]. When it comes to non-Hermitian systems, stable edge states could also exist at the interface between topological and trivial phases [54][55][56][57][58][59][60][61][62]. These topological states, originated from bulk topologies, are immune to local symmetry-preserved perturbations.…”

Section: Non-hermitian Hamiltonian Captures Essentials Of Open Systemmentioning

confidence: 99%

Symmetry-protected localized states at defects in non-Hermitian systems

Hou

2019

Phys. Rev. A

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Understanding how local potentials affect system eigenmodes is crucial for experimental studies of nontrivial bulk topology. Recent studies have discovered many exotic and highly non-trivial topological states in non-Hermitian systems. As such, it would be interesting to see how non-Hermitian systems respond to local perturbations. In this work, we consider chiral and particlehole -symmetric non-Hermitian systems on a bipartite lattice, including SSH model and photonic graphene, and find that a disordered local potential could induce bound states evolving from the bulk. When the local potential on a single site becomes infinite, which renders a lattice vacancy, chiral-symmetry-protected zero-energy mode and particle-hole symmetry-protected bound states with purely imaginary eigenvalues emerge near the vacancy. These modes are robust against any symmetry-preserved perturbations. Our work generalizes the symmetry-protected localized states to non-Hermitian systems.

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“…Open systems ubiquitously exist in physics [8][9][10], particularly, the optical and photonic systems; these are mostly non-Hermitian because they interact with the environment [11][12][13][14][15][16]. Currently, topological systems extend into the non-Hermitian region , and the nontrivial topological properties are studied in one-dimensional (1D), twodimensional (2D), and three-dimensional (3D) systems, including the Su-Schrieffer-Heeger (SSH) model [45][46][47][48][49], Aubry-André-Harper (AAH) model [50][51][52][53][54][55], Rice-Mele (RM) model [56,57], Chern insulator [58][59][60][61][62], and Weyl semimetal [63,64].…”

Section: Introductionmentioning

confidence: 99%

Inversion symmetric non-Hermitian Chern insulator

Jin

Song

2019

Phys. Rev. B

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We propose a two-dimensional non-Hermitian Chern insulator with inversion symmetry, which is anisotropic and has staggered gain and loss in both x and y directions. In this system, conventional bulk-boundary correspondence holds. The Chern number is a topological invariant that accurately predicts the topological phase transition and the existence of helical edge states in the topologically nontrivial phase. The band touching points are isolated and protected by the symmetry. The band touching affects the existence of helical edge states. Moreover, topologically protected helical edge states exist in the gapless phase for the system under open boundary condition in one direction. The detaching points between the edge states and the bulk states are predicted by the winding number associated with the vector field of average values of Pauli matrices. The non-Hermiticity also supports a topological phase with zero Chern number, where a pair of in-gap helical edge states exists. Our findings provide insights into the symmetry protected non-Hermitian topological insulators.

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Effects of non-Hermiticity on Su-Schrieffer-Heeger defect states

Cited by 69 publications

References 48 publications

Bulk-boundary correspondence in a non-Hermitian system in one dimension with chiral inversion symmetry

Bulk-boundary correspondence in a non-Hermitian system in one dimension with chiral inversion symmetry

Symmetry-protected localized states at defects in non-Hermitian systems

Inversion symmetric non-Hermitian Chern insulator

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