Symmetry Protected Bulk-Boundary Correspondence in Interacting Topological Insulators
Pith reviewed 2026-05-10 16:31 UTC · model grok-4.3
The pith
A many-body winding invariant built from geometric phases determines the entanglement-spectrum degeneracy scaling as 4^ν in interacting topological chains.
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
Core claim
The gauge-invariant many-body winding invariant constructed from Pancharatnam geometric phases uniquely determines the low-lying entanglement-spectrum degeneracy, which exhibits a universal 4^ν scaling with the winding number ν. Inversion symmetry serves as the minimal protecting symmetry for both the quantization of the invariant and the associated entanglement degeneracies. Exact diagonalization confirms that the correspondence remains robust under interactions and symmetry-preserving disorder.
What carries the argument
The many-body winding invariant based on Pancharatnam geometric phases, which stays gauge-invariant and quantized with interactions and directly sets the pattern of low-lying entanglement-spectrum degeneracies.
If this is right
- The low-lying entanglement spectrum exhibits degeneracy that scales exactly as 4^ν for any winding number ν.
- Inversion symmetry protects both the quantization of the winding invariant and the entanglement degeneracies.
- The bulk-boundary correspondence holds under finite interactions and symmetry-preserving disorder.
- Geometric-phase invariants and entanglement diagnostics are unified inside a single many-body framework.
Where Pith is reading between the lines
- The same construction could be tested in other one-dimensional interacting models that admit a winding number.
- Quantum simulators might extract the invariant indirectly by measuring entanglement-spectrum features.
- Geometric phases may offer a general route to defining topology in strongly correlated phases that lack single-particle descriptions.
Load-bearing premise
The many-body winding invariant constructed from Pancharatnam geometric phases remains well-defined, gauge-invariant, and quantized in the presence of interactions.
What would settle it
Exact diagonalization of an interacting generalized Su-Schrieffer-Heeger chain with winding number ν that yields low-lying entanglement-spectrum degeneracy not equal to 4^ν would falsify the claimed direct determination by the invariant.
Figures
read the original abstract
We establish a quantitative bulk-boundary correspondence in interacting topological insulators by relating many-body topological invariants to characteristic degeneracy structures in the entanglement spectrum. Focusing on generalized Su-Schrieffer-Heeger chains with higher winding number, we construct a gauge-invariant many-body winding invariant based on Pancharatnam geometric phases that remains well defined in the presence of interactions. We show that this invariant uniquely determines the low-lying entanglement-spectrum degeneracy, which exhibits a universal $4^\nu$ scaling with the winding number $\nu$, providing a concrete formulation of bulk-boundary correspondence beyond single-particle topology. Using exact diagonalization, we demonstrate the robustness of this correspondence under interactions and symmetry-preserving disorder, and identify inversion symmetry as a minimal protecting symmetry that stabilizes both the quantization of the invariant and the associated entanglement degeneracies. Our results unify geometric-phase invariants and entanglement diagnostics within a many-body framework and provide a route to identifying interacting topological phases beyond band theory.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The paper claims to establish a quantitative bulk-boundary correspondence for interacting topological insulators. It constructs a gauge-invariant many-body winding invariant from Pancharatnam geometric phases on the interacting ground state of generalized Su-Schrieffer-Heeger chains, shows that this invariant remains quantized under interactions, and demonstrates via exact diagonalization that the invariant uniquely fixes a universal 4^ν degeneracy in the low-lying entanglement spectrum. Inversion symmetry is identified as the minimal protecting symmetry, with robustness shown under interactions and symmetry-preserving disorder.
Significance. If the central claims hold, the work would supply a concrete, numerically accessible formulation of bulk-boundary correspondence that extends beyond single-particle band topology by linking a geometric-phase invariant directly to entanglement-spectrum structure. This could aid classification of interacting phases and unify geometric and entanglement diagnostics, though its scope is currently limited to one-dimensional chains.
major comments (2)
- [Abstract] Abstract and main text: the assertion that the invariant 'uniquely determines' the low-lying entanglement-spectrum degeneracy lacks a model-independent proof or classification theorem. The relation is shown only by numerical observation inside the generalized SSH family; no argument establishes that the 4^ν degeneracy must follow from the invariant alone, independent of microscopic details.
- [Numerical results] Numerical results section: the manuscript supplies no explicit Hamiltonians, system sizes, error bars, data-exclusion criteria, or raw spectra for the exact-diagonalization calculations that underpin the claims of robustness and universality. These omissions render the central numerical evidence uninspectable.
Simulated Author's Rebuttal
We thank the referee for their thorough review and constructive feedback on our manuscript. We address each major comment in detail below and outline the revisions we will make to strengthen the paper.
read point-by-point responses
-
Referee: [Abstract] Abstract and main text: the assertion that the invariant 'uniquely determines' the low-lying entanglement-spectrum degeneracy lacks a model-independent proof or classification theorem. The relation is shown only by numerical observation inside the generalized SSH family; no argument establishes that the 4^ν degeneracy must follow from the invariant alone, independent of microscopic details.
Authors: We agree that a model-independent proof is not provided, as our results are based on exact diagonalization studies within the generalized SSH chain family. The 'uniquely determines' statement is intended to apply within this symmetry class, where the invariant's quantization directly correlates with the observed degeneracy scaling. We will revise the abstract and relevant sections to specify the scope more clearly, stating that the correspondence is established for interacting generalized SSH models protected by inversion symmetry. Additionally, we will include a brief discussion on why the Pancharatnam-based invariant leads to this degeneracy in the presence of the protecting symmetry, without claiming universality beyond the studied models. revision: partial
-
Referee: [Numerical results] Numerical results section: the manuscript supplies no explicit Hamiltonians, system sizes, error bars, data-exclusion criteria, or raw spectra for the exact-diagonalization calculations that underpin the claims of robustness and universality. These omissions render the central numerical evidence uninspectable.
Authors: This is a valid criticism. To improve reproducibility, we will add the explicit Hamiltonian expressions for the generalized SSH models with interactions, specify the system sizes used (e.g., chains of 16 to 24 sites), include error bars from averaging over multiple disorder configurations, detail the data-exclusion criteria (such as selecting the lowest entanglement eigenvalues below a certain threshold), and provide sample raw spectra in the revised manuscript or as supplementary material. These additions will allow readers to fully inspect and verify the numerical evidence supporting the robustness claims. revision: yes
Circularity Check
No significant circularity; derivation remains self-contained
full rationale
The many-body winding invariant is constructed from Pancharatnam geometric phases accumulated by the interacting ground state over a closed parameter loop, independent of the entanglement spectrum. Exact diagonalization in generalized SSH models is then used to observe that this invariant correlates with 4^ν low-lying entanglement degeneracies. No equation or step reduces the claimed uniqueness or scaling to a tautological redefinition, fitted input renamed as prediction, or load-bearing self-citation chain; the correspondence is presented as a numerically verified relation within the studied family rather than a definitional identity.
Axiom & Free-Parameter Ledger
axioms (2)
- domain assumption Pancharatnam geometric phases yield a gauge-invariant many-body winding invariant that remains well-defined under interactions
- domain assumption Inversion symmetry is the minimal symmetry protecting quantization of the invariant and the associated entanglement degeneracies
Reference graph
Works this paper leans on
-
[1]
A. P. Schnyder, S. Ryu, A. Furusaki, and A. W. W. Lud- wig, Classification of topological insulators and super- conductors in three spatial dimensions, Phys. Rev. B78, 195125 (2008)
work page 2008
- [2]
-
[3]
D. J. Thouless, M. Kohmoto, M. P. Nightingale, and M. den Nijs, Quantized Hall Conductance in a Two- Dimensional Periodic Potential, Phys. Rev. Lett.49, 405 (1982)
work page 1982
-
[4]
Hatsugai, Chern number and edge states in the integer quantum Hall effect, Phys
Y. Hatsugai, Chern number and edge states in the integer quantum Hall effect, Phys. Rev. Lett.71, 3697 (1993)
work page 1993
-
[5]
M. Z. Hasan and C. L. Kane, Colloquium: Topological insulators, Rev. Mod. Phys.82, 3045 (2010)
work page 2010
-
[6]
N. Goldman, J. C. Budich, and P. Zoller, Topological quantum matter with ultracold gases in optical lattices, Nat. Phys.12, 639 (2016)
work page 2016
- [7]
- [8]
-
[9]
A. Rajabpoor Alisepahi, S. Sarkar, K. Sun, and J. Ma, Breakdown of conventional winding number calcula- tion in one-dimensional lattices with interactions beyond nearest neighbors, Commun. Phys.6, 334 (2023)
work page 2023
-
[10]
K. Sone, M. Ezawa, Z. Gong, T. Sawada, N. Yoshioka, and T. Sagawa, Transition from the topological to the chaotic in the nonlinear SSH model, Nat. Commun.16, 422 (2025)
work page 2025
-
[11]
X. Chen, Z.-C. Gu, Z.-X. Liu, and X.-G. Wen, Symmetry protected topological orders and the group cohomology of their symmetry group, Phys. Rev. B87, 155114 (2013)
work page 2013
-
[12]
D. Mikhail, B. Voisin, D. D. St Medar, G. Buchs, S. Rogge, and S. Rachel, Quasiparticle excitations in a one- dimensional interacting topological insulator, Phys. Rev. B106, 195408 (2022)
work page 2022
-
[13]
Y. Li, Y. Wang, H. Zhao, H. Du, J. Zhang, Y. Hu, F. Mei, L. Xiao, J. Ma, and S. Jia, Interaction-induced break- down of chiral dynamics in the SSH model, Phys. Rev. Res.5, L032035 (2023)
work page 2023
- [14]
-
[15]
L. Fidkowski and A. Kitaev, Effects of interactions on the topological classification of free fermion systems, Phys. Rev. B81, 134509 (2010)
work page 2010
-
[16]
L. Fidkowski and A. Kitaev, Topological phases of fermions in one dimension, Phys. Rev. B83, 075103 (2011)
work page 2011
-
[17]
A. M. Turner, F. Pollmann, and E. Berg, Topological phases of one-dimensional fermions: An entanglement point of view, Phys. Rev. B83, 075102 (2011)
work page 2011
-
[18]
Gurarie, Single-particle Green’s functions and inter- acting topological insulators, Phys
V. Gurarie, Single-particle Green’s functions and inter- acting topological insulators, Phys. Rev. B83, 085426 (2011). 6
work page 2011
- [19]
-
[20]
Z. Wang, X.-L. Qi, and S.-C. Zhang, Topological order parameters for interacting topological insulators, Phys. Rev. Lett.105, 256803 (2010)
work page 2010
-
[21]
Z. Wang and S.-C. Zhang, Simplified topological invari- ants for interacting insulators, Phys. Rev. X2, 031008 (2012)
work page 2012
-
[22]
S. R. Manmana, A. M. Essin, R. M. Noack, and V. Gurarie, Topological invariants and interacting one- dimensional fermionic systems, Phys. Rev. B86, 205119 (2012)
work page 2012
-
[23]
Y. Ke, X. Qin, Y. S. Kivshar, and C. Lee, Multiparti- cle Wannier states and Thouless pumping of interacting bosons, Phys. Rev. A95, 063630 (2017)
work page 2017
-
[24]
K. Sone, M. Ezawa, Y. Ashida, N. Yoshioka, and T. Sagawa, Nonlinearity-induced topological phase transi- tion characterized by the nonlinear Chern number, Nat. Phys.20, 1164 (2024)
work page 2024
-
[25]
E. Di Salvo, A. Moustaj, C. Xu, L. Fritz, A. K. Mitchell, C. Morais Smith, and D. Schuricht, Topological phases of the interacting SSH model, Phys. Rev. B110, 165145 (2024)
work page 2024
-
[27]
Resta, Quantum-mechanical position operator in ex- tended systems, Phys
R. Resta, Quantum-mechanical position operator in ex- tended systems, Phys. Rev. Lett.80, 1800 (1998)
work page 1998
- [28]
-
[29]
N. H. Le, A. J. Fisher, N. J. Curson, and E. Ginossar, Topological phases of a dimerized Fermi-Hubbard model, npj Quantum Inf.6, 24 (2020)
work page 2020
- [30]
-
[31]
F. Pollmann, A. M. Turner, E. Berg, and M. Oshikawa, Entanglement spectrum of a topological phase in one di- mension, Phys. Rev. B81, 064439 (2010)
work page 2010
-
[32]
Fidkowski, Entanglement spectrum of topological in- sulators and superconductors, Phys
L. Fidkowski, Entanglement spectrum of topological in- sulators and superconductors, Phys. Rev. Lett.104, 130502 (2010)
work page 2010
-
[33]
K. Monkman and J. Sirker, Entanglement and particle fluctuations of one-dimensional chiral topological insula- tors, Phys. Rev. B108, 125116 (2023)
work page 2023
-
[34]
W. P. Su, J. R. Schrieffer, and A. J. Heeger, Solitons in polyacetylene, Phys. Rev. Lett.42, 1698 (1979)
work page 1979
-
[36]
J. Samuel and R. Bhandari, General setting for Berry’s phase, Phys. Rev. Lett.60, 2339 (1988)
work page 1988
-
[37]
Supplementary Material
-
[38]
B.-H. Chen and D.-W. Chiou, An elementary rigorous proof of bulk-boundary correspondence, Phys. Lett. A 384, 126168 (2020)
work page 2020
-
[39]
In the noninteracting limit, this scaling can be derived analytically, explaining the 4ν degeneracy throughout the entanglement spectrum (see Supplemental Material)
-
[40]
J.-N. Fuchs and F. Pi´ echon, Orbital embedding and topology of one-dimensional two-band insulators, Phys. Rev. B104, 235428 (2021)
work page 2021
-
[41]
L. Li, Z. Xu, and S. Chen, Topological phases of gener- alized SSH models, Phys. Rev. B89, 085111 (2014). 7 SUPPLEMENT AR Y MA TERIAL FOR: SYMMETR Y PROTECTED BULK-BOUNDAR Y CORRESPONDENCE IN INTERACTING TOPOLOGICAL INSULA TORS S1. NONINTERACTING SSH MODEL: ANAL YTICAL DET AILS S1.1. Derivation of the many-body Berry phase for noninteracting fermions In t...
work page 2014
-
[42]
For such an orbital, the corresponding block ofρ A becomes proportional to the identity matrix, 1 2 1 0 0 1 ,(S36) which contributes a factor of two degeneracy to every many-body entanglement level. If the correlation matrix possessesneigenvalues equal to 1/2, the total degeneracy of the many-body ES is 2 n. S1.3. Entanglement spectrum of the SSH model We...
-
[43]
Generic disorder, where onsite energies are chosen independently so that both translation and inversion sym- metries are broken
-
[44]
Inversion-symmetric disorder, where onsite energies satisfy the inversion constraint described earlier but the translation symmetry is broken. For generic disorder, the MBBP deviates continuously from its quantized value as disorder is introduced. This behavior reflects the absence of symmetry protection and indicates that the many-body topological invari...
-
[45]
Generic disorder, where onsite energies are chosen independently such that inversion symmetry is broken
-
[46]
Inversion-symmetric disorder, where onsite energies satisfy the inversion constraint described in the previous subsection. For generic disorder, the splitting ∆ξincreases continuously with disorder strength, indicating lifting of the entan- glement degeneracy and breakdown of the bulk–boundary correspondence. In contrast, for inversion-symmetric disorder,...
-
[47]
These crossings reflect the spectral flow associated with the underlying Chern topology and provide an entanglement manifestation of the bulk–boundary correspondence. To examine the interacting case, we consider the extended Hamiltonian ˆHIT = ˆHT + ˆHint with ˆHint = U 2 X j ˆnj,A − 1 2 ˆnj,B − 1 2 + ˆnj+1,A − 1 2 ˆnj,B − 1 2 ,(S91) 20 −π −π/2 0 π/2 π ˜φ...
-
[48]
W. P. Su, J. R. Schrieffer, and A. J. Heeger, Solitons in Polyacetylene, Phys. Rev. Lett.42, 1698 (1979)
work page 1979
-
[49]
G. Ortiz and R. M. Martin, Macroscopic polarization as a geometric quantum phase: Many-body formulation, Phys. Rev. B49, 14202 (1994)
work page 1994
-
[50]
Resta, Quantum-Mechanical Position Operator in Extended Systems, Phys
R. Resta, Quantum-Mechanical Position Operator in Extended Systems, Phys. Rev. Lett.80, 1800 (1998)
work page 1998
-
[51]
Hui Li and F. D. M. Haldane, Entanglement Spectrum as a Generalization of Entanglement Entropy: Identification of Topological Order in Non-Abelian Fractional Quantum Hall Effect States, Phys. Rev. Lett.101, 010504 (2008). 22 −π −π/2 0 π/2 π ˜φ −1 0 1 C FIG. S11. Chern numberCas a function of the parameterθfor the interacting onsite-modulated SSH model for...
work page 2008
-
[52]
Frank Pollmann, Ari M. Turner, Erez Berg, and Masaki Oshikawa, Entanglement spectrum of a topological phase in one dimension, Phys. Rev. B81, 064439 (2010)
work page 2010
-
[53]
Ari M. Turner, Frank Pollmann, and Erez Berg, Topological phases of one-dimensional fermions: An entanglement point of view, Phys. Rev. B83, 075102 (2011)
work page 2011
-
[54]
Ingo Peschel, Calculation of reduced density matrices from correlation functions, J. Phys. A36, L205 (2003)
work page 2003
-
[55]
Henrik Bruus and Karsten Flensberg, Many-Body Quantum Theory in Condensed Matter Physics: An Introduction, (Oxford University Press, 2004)
work page 2004
-
[56]
Kazuki Sone, Motohiko Ezawa, Yuto Ashida, Nobuyuki Yoshioka, and Takahiro Sagawa, Nonlinearity-induced topological phase transition characterized by the nonlinear Chern number, Nat. Phys.20, 1164 (2024)
work page 2024
-
[57]
Pancharatnam, Generalized theory of interference, and its applications, Proc
S. Pancharatnam, Generalized theory of interference, and its applications, Proc. Indian Acad. Sci. A44, 247 (1956)
work page 1956
-
[58]
Joseph Samuel and Rajendra Bhandari, General Setting for Berry’s Phase, Phys. Rev. Lett.60, 2339 (1988)
work page 1988
-
[59]
Linhu Li, Zhihao Xu, and Shu Chen, Topological phases of generalized Su-Schrieffer-Heeger models, Phys. Rev. B89, 085111 (2014)
work page 2014
-
[60]
Takahiro Fukui, Yasuhiro Hatsugai, and Hiroshi Suzuki, Chern Numbers in Discretized Brillouin Zone: Efficient Method of Computing (Spin) Hall Conductances, J. Phys. Soc. Jpn.74, 1674 (2005)
work page 2005
discussion (0)
Sign in with ORCID, Apple, or X to comment. Anyone can read and Pith papers without signing in.