Hybrid skin-topological modes without asymmetric couplings

Abstract

Non-Hermitian skin effect (NHSE) in non-Hermitian lattice systems, associated with a point gap on the complex energy plane, has attracted great theoretical and experimental interest. Much less is studied on the so-called second-order non-Hermitian skin effect, where the bulk does not support a point gap but localization at the corner still occurs. This work discovers a class of hybrid skin-topological modes as the second-order non-Hermitian skin effect without asymmetric couplings. Specifically, by only adding gain/loss to two-dimensional Chern insulators and so long as the gain/loss strength does not close the line gap, all the topological edge states are localized at one corner under the open boundary condition, with the bulk states extended. The resultant non-Hermitian Chern bands can be still topologically characterized by Chern numbers, whereas the hybrid skin-topological modes are understood via some auxiliary Hermitian systems that belong to either intrinsic or extrinsic second-order topological insulator phases. By proposing an innovative construction of auxiliary Hamiltonian, our generic route to hybrid skin-topological modes is further successfully extended to nonequilibrium topological systems with gain and loss, where the anomalous Floquet band topology is no longer captured by band Chern numbers. The extension thus leads to the intriguing finding of nonequilibrium hybrid skin-topological modes. In addition to offering a straightforward route to experimental realization of hybrid topological-skin effects, this study also opens up a promising perspective for the understanding of corner localization by revealing the synergy of three important concepts, namely, non-Hermitian topological insulator, second-order non-Hermitian skin effect, and second-order topological insulator.

10+ pages with 9 figures. Comments are welcome

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Cited by in corpus (41)

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• Enhancement of Second-Order Non-Hermitian Skin Effect by Magnetic Fields
• Non-Bloch bands in two-dimensional non-Hermitian systems
• Non-Hermitian Floquet Topological Matter -- A Review
• Non-Hermitian Chiral Skin Effect
• Hermitian Bulk -- Non-Hermitian Boundary Correspondence
• Photonic corner skin modes
• Loss-induced Floquet non-Hermitian skin effect
• Hybrid skin-topological effect induced by eight-site cells and arbitrary adjustment of the localization of topological edge states
• Hybrid higher-order skin-topological effect in hyperbolic lattices
• Occupation-dependent particle separation in one-dimensional non-Hermitian lattices
• Universal platform of point-gap topological phases from topological materials
• Non-Hermitian boundary spectral winding
• Generalized bulk-boundary correspondence in periodically driven non-Hermitian systems
• Mixed higher-order topology: boundary non-Hermitian skin effect induced by a Floquet bulk
• A brief review of hybrid skin-topological effect
• Direction reversal of non-Hermitian skin effect via coherent coupling
• Non-Hermitian Topology in Hermitian Topological Matter
• Non-Hermitian Skin Effect in Periodically-Driven Dissipative Ultracold Atoms
• Geometry-dependent skin effect and anisotropic Bloch oscillations in a non-Hermitian optical lattice
• Non-Hermitian second-order topological superconductors
• Braiding Topology of Non-Hermitian Open-Boundary Bands
• Non-Hermitian topological phases and skin effects in kagome lattices
• Entanglement phase transitions in non-Hermitian Floquet systems
• Nontrivial worldline winding in non-Hermitian quantum systems
• Investigation of a non-Hermitian edge burst with time-dependent perturbation theory
• Extended imaginary gauge transformation in a general nonreciprocal lattice
• Interaction-Induced Second-Order Skin Effect
• Non-Hermitian Skin Effect Along Hyperbolic Geodesics
• Inner non-Hermitian skin effect on Bethe lattice
• Dissipation Enhanced Unidirectional Transport in Topological Systems
• Multiple topological transitions and spectral singularities in non-Hermitian Floquet systems
• Anisotropic-scaling localization in higher-dimensional non-Hermitian systems
• Topologically compatible non-Hermitian skin effect
• Hermitian and non-Hermitian topology in active matter
• Topological and fractal defect states in non-Hermitian lattices
• Unified Multipole Bott Indices for Non-Hermitian Skin Effect in Different Orders
• Magnetic Control of the Non-Hermitian Skin Effect in Two-Dimensional Lattices
• Non-Hermitian higher-order topological insulators enabled by altermagnet engineering
• Hybrid Higher-Order Skin Topological Modes in the Two-Dimensional Su-Schrieffer-Heeger Model with Nonreciprocal Hoppings
• Bulk-edge coulping induced by a moving impurity