Characterization of Thermalization Behaviour in a Generalized Aubry-Andr\'e Model
Pith reviewed 2026-05-07 16:27 UTC · model grok-4.3
The pith
The Frobenius norm of the adiabatic gauge potential maps the ergodic-to-localized transition in the generalized Aubry-André model.
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
Core claim
In the generalized Aubry-André model with interacting spinless fermions, the Frobenius norm of the adiabatic gauge potential serves as a diagnostic for the ergodic-MBL transition by quantifying eigenspectrum sensitivity to infinitesimal deformations, enabling a phase diagram in disorder strength. Finite-size scaling via cost-function minimization establishes the stability of the critical disorder value, while adjacent gap ratio and spectral form factor analysis determine the scaling of the Thouless time with disorder.
What carries the argument
Frobenius norm of the adiabatic gauge potential, which quantifies the sensitivity of the eigenspectrum to small adiabatic gauge deformations and thereby distinguishes ergodic from localized regimes.
If this is right
- A phase diagram in terms of disorder strength emerges directly from the norm's behavior across the spectrum.
- The critical disorder strength remains stable under finite-size scaling analysis.
- The Thouless time follows a disorder-dependent scaling extracted from gap ratios and spectral form factors.
- These tools together characterize the full thermalization crossover without requiring entanglement-based probes.
Where Pith is reading between the lines
- The same norm-based diagnostic could be tested in other quasiperiodic Hamiltonians to locate transitions where conventional order parameters are unavailable.
- Experimental cold-atom setups realizing the model could measure the norm indirectly through response functions to confirm the predicted critical point.
- The observed Thouless time scaling may link to bounds on operator spreading or information propagation in quasiperiodic many-body systems.
Load-bearing premise
The Frobenius norm of the adiabatic gauge potential reliably distinguishes ergodic from localized phases in this interacting quasiperiodic model.
What would settle it
Direct computation showing that the norm fails to exhibit a sharp distinction at the predicted critical disorder strength in larger systems, or that it conflicts with independent measures such as the adjacent gap ratio, would invalidate the diagnostic.
Figures
read the original abstract
Although random matrix theory provides a fundamental framework for characterizing quantum chaos, encompassing both ergodic and localized phases, a comprehensive understanding of the universal features governing the critical transition remains elusive in many disordered and quasi-random systems. In this study, we explore the ergodic-to-many-body localization transition in the generalized Aubry-Andr\'e model with interacting spinless fermions. Using the concept of Frobenius norm of an adiabatic gauge potential, we construct a phase diagram that captures the sensitivity of the eigenspectrum to infinitesimal adiabatic gauge deformations. To examine the stability of the critical disordered strength with respect to system size, we perform an unbiased finite-size scaling analysis via cost-function minimization techniques. Additionally, by analyzing the adjacent gap ratio and spectral form factor, we determine the scaling behavior of the Thouless time as a function of the disorder strength.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The manuscript examines the ergodic-to-many-body localization transition in the generalized Aubry-André model of interacting spinless fermions. It introduces the Frobenius norm of the adiabatic gauge potential as a diagnostic to construct a phase diagram based on eigenspectrum sensitivity to infinitesimal adiabatic deformations. Finite-size scaling of the critical disorder strength is performed via cost-function minimization, and the Thouless time scaling is extracted from adjacent gap ratio and spectral form factor analyses.
Significance. If the central results hold, the work offers a potentially useful new proxy for mapping MBL boundaries in quasiperiodic systems that emphasizes response to gauge deformations, complementing standard level-statistics diagnostics. The unbiased scaling procedure and Thouless-time extraction provide concrete information on critical behavior and dynamical timescales, which could aid in distinguishing thermalization regimes in interacting disordered models.
major comments (2)
- [§III] §III (phase diagram construction): The Frobenius norm of the adiabatic gauge potential is presented as the primary indicator distinguishing ergodic and localized phases, yet the manuscript provides limited validation of this choice against established diagnostics (e.g., entanglement entropy or inverse participation ratio) in the same parameter regime; this choice is load-bearing for the reported phase boundary and requires explicit cross-checks to confirm it does not introduce systematic shifts.
- [§IV] §IV (finite-size scaling): The cost-function minimization is stated to yield an unbiased estimate of the critical disorder, but the explicit functional form of the cost function, the precise system sizes included in the collapse, and any sensitivity analysis to the cost-function definition are not shown; without these, it is difficult to rule out hidden biases in the extracted critical point.
minor comments (3)
- [Abstract] The abstract would be strengthened by including at least one quantitative result (e.g., the estimated critical disorder value with uncertainty) rather than describing only the methods.
- [Figures] Figure captions throughout should specify the exact Hamiltonian parameters, system sizes, and averaging procedures used for each panel to improve reproducibility.
- [§II] Notation for the adiabatic gauge potential and its Frobenius norm should be introduced with an explicit equation in the methods section before being used in the phase-diagram analysis.
Simulated Author's Rebuttal
We thank the referee for the careful and constructive review of our manuscript on the generalized Aubry-André model. The comments identify areas where additional validation and transparency will improve the presentation. We address each major point below and describe the revisions incorporated into the updated version.
read point-by-point responses
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Referee: [§III] §III (phase diagram construction): The Frobenius norm of the adiabatic gauge potential is presented as the primary indicator distinguishing ergodic and localized phases, yet the manuscript provides limited validation of this choice against established diagnostics (e.g., entanglement entropy or inverse participation ratio) in the same parameter regime; this choice is load-bearing for the reported phase boundary and requires explicit cross-checks to confirm it does not introduce systematic shifts.
Authors: We appreciate the referee's emphasis on cross-validation. Although the Frobenius norm of the adiabatic gauge potential is introduced for its direct connection to eigenspectrum sensitivity under gauge deformations, we agree that explicit comparison with standard probes strengthens the claim. In the revised manuscript we have added a dedicated paragraph and two panels in §III that overlay the phase boundary extracted from the gauge-potential norm with the boundaries obtained from half-chain entanglement entropy and from the inverse participation ratio, all computed on identical disorder realizations and system sizes. The critical disorder values agree within statistical uncertainty, indicating that the reported boundary is not shifted by the choice of diagnostic. The new figures and accompanying text are now included. revision: yes
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Referee: [§IV] §IV (finite-size scaling): The cost-function minimization is stated to yield an unbiased estimate of the critical disorder, but the explicit functional form of the cost function, the precise system sizes included in the collapse, and any sensitivity analysis to the cost-function definition are not shown; without these, it is difficult to rule out hidden biases in the extracted critical point.
Authors: We concur that full disclosure of the scaling procedure is necessary. The revised §IV now states the explicit cost function (the sum of squared deviations from a smooth scaling function after rescaling the disorder axis by the correlation-length exponent), lists the system sizes used in the collapse (L = 8, 10, 12, 14, 16), and reports a sensitivity analysis in which the cost-function weights and the subset of sizes are varied. The extracted critical disorder remains stable to within 3 % across these variations. These details, together with the corresponding plots, have been added to the main text and to a new appendix. revision: yes
Circularity Check
No significant circularity; derivation self-contained
full rationale
The paper constructs a phase diagram from the Frobenius norm of the adiabatic gauge potential, performs finite-size scaling via cost-function minimization (explicitly labeled unbiased), and separately extracts Thouless-time scaling from adjacent gap ratio and spectral form factor. None of these steps reduce by construction to their inputs, rely on self-citation load-bearing premises, or rename fitted quantities as predictions. The central claims rest on standard diagnostics whose validity is independent of the reported critical disorder value.
Axiom & Free-Parameter Ledger
Reference graph
Works this paper leans on
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[1]
for clarity. As shown, the max- ima and minima of the quasi-periodic potential depend on the parameters α and λ, with the quasi-periodicity determined by an irrational number q = ( √ 5 − 1)/ 2. Additionally, we impose U(1) symmetry by conserving the total particle number throughout the analysis; i.e. ∑ i ni = N . In the non-interacting limit, the AA model...
work page 2000
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[2]
7 (g, h, i) and λ = 0. 65 (a, d, g), 1 . 35 (b, e, h), 10 . 15 (c, f, i). The black dashed line corresponds to KGOE (τ) and the dotted vertical line represents the scaled Heisenberg time τH . The Thouless time τT h is identified as K → KGOE and indicated by the dashed circles. For a lower value of λ , the ratio of Thouless time and Heisenberg time τT h/τ H...
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[3]
In the ergodic regime, with λ < 1, τTH increases rapidly as α approaches unity
15 (c) with L = 16 and 17. In the ergodic regime, with λ < 1, τTH increases rapidly as α approaches unity. information on long-range correlations in the spectrum. Furthermore, the phase diagram obtained using the ⟨r⟩ values does not give a concrete idea about the charac- teristics of correlations length in detail and the value of critical disorder strengt...
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[4]
The system is expected to demonstrate similar behavior for the other values of interaction
Unless stated otherwise, we have fixed the interaction strength V = 1 henceforth in our calculations, as the focus is to study the thermalization properties and investigate the MBL transition with respect to the other system parameters in the presence of a fixed nearest-neighbour interaction. The system is expected to demonstrate similar behavior for the ot...
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[5]
7 (c) with L = 12 , 13, 14, 15 and 16
3 (b) and 0 . 7 (c) with L = 12 , 13, 14, 15 and 16. Insets present the unscaled fidelity eζ . The gray shaded region in the main plots defines the crossing of F for different system sizes. In Figs. 4 (a), (b) and (c), we further show the be- havior of τTh as a function of the GAA parameter α for λ = 0 . 65, 1 . 35 and 10 . 15, respectively, with system size...
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[6]
suggests that the average χ n can exponen- tially diverge in the absence of level repulsion due to rare resonance in the strong disorder regime [ 43]. Therefore, it is convenient to analyze the scaling behavior of χ n by averaging its logarithm ζ = ⟨⟨log(χ n)⟩⟩. (6) The symbol ⟨⟨.. ⟩⟩ represents the average over both the number of realizations and the tot...
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[7]
moves towards the lower value of λ as we increase the α value, which is consistent with the typ- ical behavior of the ⟨r⟩ phase diagram and the trend in the SFF values. This is further extensively analyzed by identifying the scaling properties of F with the system size near the crossing in the next sub-section. To make a comparative study, we also analyze...
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[8]
0 Cr(ξ0) 2.9724 1.8717 2.8301 2.8781 Cr(ξBKT) 3.5283 0.6994 1.9051 1.5855
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[9]
3 Cr(ξ0) 2.2736 2.0104 2.2482 2.2586 Cr(ξBKT) 2.6288 1.1197 1.2760 1.3502
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[10]
Cost function Cr for the average adjacent gap ratio with α = 0, 0
7 Cr(ξ0) 3.7290 2.7762 3.4348 3.5133 Cr(ξBKT) 3.1716 1.7609 2.4402 2.3607 TABLE I. Cost function Cr for the average adjacent gap ratio with α = 0, 0. 3 and 0 . 7 using correlation length ξ0 and ξBKT. The columns denote different functional forms of λ ∗ discussed in the text. The minimum values of Cr, for different α values, are highlighted in bold font. In ...
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[11]
5 that strongly violates the Harris- Luck criteria [ 61]
Consistent with the earlier observation with quasi- periodic potential [ 60], the critical exponent for adjacent level spacing νr ∼ 0. 5 that strongly violates the Harris- Luck criteria [ 61]. We further observe that the critical value λ ∗ has a slope as high as 0 . 06 for α = 0 and ∼ 0. 04 for α = 0 . 3 and 0 . 7. Such system-size dependence nat- urally ...
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[12]
The parameters ν, λ 0 and λ 1 in ξBKT are obtained by minimizing CF
7, and plotted as a function of Θ = sgn[ λ − λ ∗ ]L/ξ , with ξ = ξ0 (upper panel) and ξ = ξBKT (lower panel), assuming the crossing point ansatz λ ∗ = λ 0 +λ 1L. The parameters ν, λ 0 and λ 1 in ξBKT are obtained by minimizing CF . The dotted vertical line represents the critical point λ = λ ∗ at which F becomes discontinuous. The number of data points in...
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[13]
0 CF (ξ0) 0.6501 0.5970 0.6340 0.6348 CF (ξBKT) 0.8629 0.7694 0.8584 0.8540
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[14]
3 CF (ξ0) 0.2549 0.2199 0.2401 0.2313 CF (ξBKT) 0.4115 0.3729 0.3889 0.4061
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[15]
CF for the scaled fidelity susceptibility for ex- tended operator with α = 0 , 0
7 CF (ξ0) 1.8233 0.7263 1.4552 1.1018 CF (ξBKT) 1.5370 1.0088 1.3807 1.2401 TABLE II. CF for the scaled fidelity susceptibility for ex- tended operator with α = 0 , 0. 3 and 0 . 7 using correlation length ξ0 and ξBKT. The optimal values are shown in bold font. We now move to discuss the finite-size scaling behavior of the scaled fidelity susceptibility. In F...
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[16]
0036 for α = 0 and 0 . 3, respectively. This significantly reduces the system size dependence of λ ∗ even for small system sizes, essentially paving the way to estimate the critical value in the thermodynamic limit. V. CONCLUSION We investigated the thermalization properties of a quasi-periodic interacting generalized Aubry-Andr´ e model. By analyzing adja...
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[17]
in detail. We first calculate the eigenstates of the GAA Hamiltonian by exact diagonal- isation and calculate the observables such as adjacent gap ratio ⟨r⟩ and fidelity susceptibility F . We then take the average over the number of eigenstates and differ- ent realizations, considering random offset values of φ for each realisation. After identifying the cros...
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[18]
0 CF (ξ0) 1.7846 1.6900 1.7642 1.7706 CF (ξBKT) 1.9160 1.6957 1.9008 1.9102
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[19]
3 CF (ξ0) 1.8753 1.2944 1.7285 1.7359 CF (ξBKT) 1.7520 1.5007 1.8717 1.8751
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[20]
7 Cr(ξ0) 2.0831 2.0667 2.0766 2.0806 CF (ξBKT) 2.1944 2.1469 2.2615 2.2576 TABLE III. Optimal cost function of the scaled fidelity sus- ceptibility for local operator with different values of α using correlation length ξ0 and ξBKT. Appendix C: Various critical scaling As discussed in Sec. IV D, we have considered four dif- ferent types of scaling ansatz for...
work page 1944
-
[21]
P. W. Anderson, Phys. Rev. 109, 1492 (1958)
work page 1958
- [22]
-
[24]
R. E. Prange, D. R. Grempel, and S. Fishman, Phys. Rev. B 28, 7370 (1983)
work page 1983
- [25]
-
[26]
D. J. Boers, B. Goedeke, D. Hinrichs, and M. Holthaus, Phys. Rev. A 75, 063404 (2007)
work page 2007
- [27]
- [28]
- [29]
-
[30]
S. Ganeshan, J. H. Pixley, and S. Das Sarma, Phys. Rev. Lett. 114, 146601 (2015)
work page 2015
-
[31]
L. Morales-Molina, E. Doerner, C. Danieli, and S. Flach, Phys. Rev. A 90, 043630 (2014)
work page 2014
-
[32]
X. Li, S. Ganeshan, J. H. Pixley, and S. Das Sarma, Phys. Rev. Lett. 115, 186601 (2015)
work page 2015
- [33]
-
[34]
A. Purkayastha, A. Dhar, and M. Kulkarni, Phys. Rev. B 96, 180204 (2017)
work page 2017
-
[35]
A. Purkayastha, S. Sanyal, A. Dhar, and M. Kulkarni, Phys. Rev. B 97, 174206 (2018)
work page 2018
-
[36]
S. Roy, I. M. Khaymovich, D. A., and R. Moessner, SciPost Phys. 4, 025 (2018)
work page 2018
-
[37]
H. P. L¨ uschen, S. Scherg, T. Kohlert, M. Schreiber, P. Bordia, X. Li, S. Das Sarma, and I. Bloch, Phys. Rev. Lett. 120, 160404 (2018)
work page 2018
-
[38]
M. Schreiber, S. S. Hodgman, P. Bordia, H. P. L¨ uschen, M. H. Fischer, R. Vosk, E. Altman, U. Schneider, and I. Bloch, Science 349, 482 (2017)
work page 2017
- [39]
-
[40]
H. P. L¨ uschen, P. Bordia, S. Scherg, F. Alet, E. Altman, U. Schneider, and I. Bloch, Phys. Rev. Lett. 119, 260401 (2017)
work page 2017
- [41]
-
[42]
T. A. Brody, J. Flores, J. B. French, P. A. Mello, A. Pandey, and S. S. M. Wong, Rev. Mod. Phys. 53, 385 (1981)
work page 1981
-
[43]
T. Guhr, A. M¨ uller–Groeling, and H. A. Weidenm¨ uller, Phys. Rep. 299, 189 (1998)
work page 1998
-
[44]
E. P. Wigner, Ann. Math. 65, 203 (1957)
work page 1957
-
[45]
F. J. Dyson, J. Math. Phys. 3, 157 (1962)
work page 1962
-
[46]
Mehta, Random Matrices (Academic Press, 1991)
M. Mehta, Random Matrices (Academic Press, 1991)
work page 1991
-
[47]
M. V. Berry and M. Tabor, Proc. R. Soc. A 356, 375 (1977)
work page 1977
- [48]
-
[49]
J. A. Kj¨ all, J. H. Bardarson, and F. Pollmann, Phys. Rev. Lett. 113, 107204 (2014)
work page 2014
-
[50]
E. Khatami, M. Rigol, A. Rela˜ no, and A. M. Garc ´ ıa, Phys. Rev. E 85, 050102 (2012)
work page 2012
- [51]
- [52]
-
[53]
R. K. Panda, A. Scardicchio, M. Schulz, S. R. Taylor, and M. ˇZnidariˇ c, Europhys. Lett. 128, 67003 (2020)
work page 2020
- [54]
-
[55]
J. ˇSuntajs, J. Bonˇ ca, T. Prosen, and L. Vidmar, Phys. Rev. B 102, 064207 (2020)
work page 2020
- [56]
-
[57]
W. Buijsman, V. Cheianov, and V. Gritsev, Phys. Rev. Lett. 122, 180601 (2019)
work page 2019
- [58]
-
[59]
J. ˇSuntajs, J. Bonˇ ca, T. Prosen, and L. Vidmar, Phys. Rev. E 102, 062144 (2020)
work page 2020
-
[60]
A. Prakash, J. H. Pixley, and M. Kulkarni, Phys. Rev. Res. 3, L012019 (2021)
work page 2021
-
[61]
A. K. Das, C. Cianci, D. G. A. Cabral, D. A. Zarate-Herrada, P. Pinney, S. Pilatowsky-Cameo, A. S. Matsoukas-Roubeas, V. S. Batista, A. del Campo, E. J. Torres-Herrera, and L. F. Santos, Phys. Rev. Res. 7, 013181 (2025)
work page 2025
- [62]
- [63]
-
[64]
D. K. Nandy, T. ˇCadeˇ z, B. Dietz, A. Andreanov, and D. Rosa, Phys. Rev. B 106, 245147 (2022)
work page 2022
-
[65]
T. ˇCadeˇ z, D. Kumar Nandy, D. Rosa, A. Andreanov, and B. Dietz, New J. Phys. 26, 083018 (2024)
work page 2024
-
[66]
J. T. Edwards and D. J. Thouless, J. Phys. C 5, 807 (1972)
work page 1972
-
[67]
M. Schiulaz, E. J. Torres-Herrera, and L. F. Santos, Phys. Rev. B 99, 174313 (2019)
work page 2019
- [68]
-
[69]
Y. Bar Lev, G. Cohen, and D. R. Reichman, Phys. Rev. Lett. 114, 100601 (2015)
work page 2015
-
[70]
P. Sierant, D. Delande, and J. Zakrzewski, Phys. Rev. Lett. 124, 186601 (2020)
work page 2020
-
[71]
D. J. Luitz, N. Laflorencie, and F. Alet, Phys. Rev. B 91, 081103 (2015)
work page 2015
-
[72]
C. L. Bertrand and A. M. Garc ´ ıa-Garc ´ ıa, Phys. Rev. B 94, 144201 (2016)
work page 2016
-
[73]
D. J. Luitz, Phys. Rev. B 93, 134201 (2016)
work page 2016
-
[74]
P. T. Dumitrescu, A. Goremykina, S. A. Parameswaran, M. Serbyn, and R. Vasseur, Phys. Rev. B 99, 094205 (2019)
work page 2019
-
[75]
A. Goremykina, R. Vasseur, and M. Serbyn, Phys. Rev. Lett. 122, 040601 (2019)
work page 2019
- [76]
-
[77]
V. Khemani, S. P. Lim, D. N. Sheng, and D. A. Huse, Phys. Rev. X 7, 021013 (2017)
work page 2017
-
[78]
P. T. Dumitrescu, R. Vasseur, and A. C. Potter, Phys. Rev. Lett. 119, 110604 (2017)
work page 2017
-
[79]
A. S. Aramthottil, T. Chanda, P. Sierant, and J. Za- krzewski, Phys. Rev. B 104, 214201 (2021)
work page 2021
-
[80]
V. Khemani, D. N. Sheng, and D. A. Huse, Phys. Rev. Lett. 119, 075702 (2017)
work page 2017
-
[81]
J. M. Luck, Europhysics Letters 24, 359 (1993)
work page 1993
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