Exploring topological phases with extended Su-Schrieffer-Heeger models
Pith reviewed 2026-05-10 17:22 UTC · model grok-4.3
The pith
The Su-Schrieffer-Heeger model supports topological phases that become more sophisticated when the model is extended in dimensionality, unit cell size, or with additional physical terms.
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
Core claim
The SSH model describes a 1D tight-binding lattice with alternating nearest-neighbor amplitudes and supports a topological phase with zero energy eigenstates localized at each end. Extensions by increasing dimensionality, enlarging the unit cell, or adding extra terms give rise to more sophisticated topological phenomena, as illustrated through case studies from existing literature where properties of topological origin are elaborated.
What carries the argument
Extended Su-Schrieffer-Heeger models obtained by modifying the original 1D alternating hopping lattice through added dimensions, larger unit cells, or physical effect terms, which carry the argument by exhibiting various boundary-localized modes and topological invariants.
If this is right
- Models with increased dimensionality support topological phases in two or more dimensions with protected edge or surface states.
- Enlarged unit cells allow for models with multiple bands and more complex topological classifications.
- Adding extra terms representing physical effects introduces new types of topological protection or phase transitions.
- These extended models provide concrete examples for studying phenomena absent in the minimal 1D SSH case.
Where Pith is reading between the lines
- The SSH framework acts as a simple base from which many known topological systems can be derived by systematic modifications.
- Experimental realizations could involve cold atoms or photonic lattices tuned to match the extended Hamiltonians.
- Further work might classify all possible extensions using symmetry indicators or topological invariants.
Load-bearing premise
That the chosen case studies from the literature cover a representative range of extensions and capture their key topological properties adequately.
What would settle it
A calculation or simulation of an extended SSH Hamiltonian showing no zero-energy boundary modes where the review predicts them would challenge the corresponding case study.
Figures
read the original abstract
The Su-Schrieffer-Heeger (SSH) model describes a tight-binding one-dimensional (1D) lattice with alternating nearest-neighbor amplitudes. Despite its mathematically simple and physically intuitive structure, the SSH model is capable of supporting a 1D topological phase that is characterized by the presence of zero energy eigenstates (zero modes) localized at each end of the lattice. For this reason, many studies in the area of topological phases of matter often consider the SSH model as a subject for various extensions that give rise to more sophisticated topological phenomena. The purpose of this article is to review, in sufficient detail, existing approaches to extending the SSH model. This includes extensions by increasing the dimensionality of the lattice, enlarging the size of its unit cell, or adding extra terms that represent various physical effects. For each approach, some extended SSH models studied in relevant existing literature are discussed as case studies. Noteworthy properties of such models, which are of topological origin, are further comprehensively elaborated.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The manuscript is a review of the Su-Schrieffer-Heeger (SSH) model and its extensions for exploring topological phases of matter. It begins by recalling that the basic 1D SSH chain supports a topological phase with zero-energy edge-localized modes, then systematically examines three classes of extensions—increasing lattice dimensionality, enlarging the unit cell, and adding extra terms that encode additional physical effects—using selected case studies drawn from the existing literature to illustrate the resulting topological phenomena and invariants.
Significance. If the coverage is balanced and the case studies are accurately summarized, the review provides a useful entry point and reference for researchers working on 1D and higher-dimensional topological insulators and superconductors. By organizing extensions around a single, well-understood parent model, it can help readers map how simple modifications generate richer phenomenology such as higher-order topology, non-Hermitian effects, or fractionalized excitations.
minor comments (3)
- The abstract states that the review covers extensions 'in sufficient detail,' yet the manuscript does not include an explicit statement of selection criteria for the case studies or a table summarizing the topological invariants and edge-state properties across all discussed models; adding such a table would improve usability.
- Several figures (e.g., those depicting band structures or edge-mode wavefunctions for the extended models) lack labels for the topological phase boundaries or the value of the relevant winding number; this reduces clarity when the text refers to 'the topological regime.'
- The reference list appears to omit a few recent works on non-Hermitian extensions of the SSH model (post-2022) that are directly relevant to the 'adding extra terms' section; a brief check against current literature would strengthen completeness.
Simulated Author's Rebuttal
We thank the referee for their positive assessment of the manuscript as a useful entry point and reference for researchers studying topological phases via extensions of the SSH model. We appreciate the recommendation for minor revision. No specific major comments were provided in the report.
Circularity Check
No significant circularity: review of external literature
full rationale
The manuscript is a review that summarizes established results on the SSH model and its extensions from the existing literature. It presents no new derivations, predictions, or fitted parameters of its own; all case studies and noteworthy topological properties are explicitly drawn from cited external works. No load-bearing step reduces by construction to self-definition, self-citation chains, or renaming of inputs. The central claims restate well-known facts (zero-energy edge modes in the topological phase) without internal circular logic.
Axiom & Free-Parameter Ledger
axioms (1)
- domain assumption The SSH model is a tight-binding 1D lattice with alternating nearest-neighbor amplitudes that supports zero-energy end states in its topological phase.
Reference graph
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Extension by changing the periodicity of the hopping amplitudes As was schematically shown in Fig. 1, the real space Hamiltonian of the SSH model consists of two alter- nating hopping amplitudesvandw. One of the most 10 FIG. 9. The single particle energy spectrum of the SSH3 model under (a,b,c) PBC and (d) OBC at varying values of w. The system parameters...
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[2]
Extension by applying a nontrivial square-root Another method for extending the SSH model is by appropriately defining a new HamiltonianH sqSSH, so that its square yields the real space Hamiltonian of the SSH model. This idea was first envisioned in Ref. [91], which considers a general tight-binding Hamiltonian for the square-root model as (in the first-q...
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