Coexistence of Anderson Localization and Quantum Scarring in Two Dimensions
Pith reviewed 2026-05-16 20:08 UTC · model grok-4.3
The pith
Finite two-dimensional disordered systems host both Anderson-localized states at low energy and scarred states at higher energy.
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
Core claim
In two-dimensional disordered systems of finite size with periodic confinement, eigenstates at low energies exhibit strong Anderson localization while a subset of higher-energy states displays variational scarring with anisotropic intensity patterns. The energy-dependent localization length and finite-size effects allow these two regimes to coexist even though scaling theory predicts eventual localization of all states in the large-system limit. This coexistence produces distinct, observable signatures in both spatial intensity patterns and spectral statistics.
What carries the argument
Energy-dependent localization length in finite-size systems with periodic confinement, which permits scarred states to survive alongside localized states.
If this is right
- Spatial intensity maps show clear deviations from random-wave expectations at higher energies.
- Spectral statistics exhibit robust, non-random features tied to the scarred subset.
- The signatures remain measurable in mesoscopic electronic, photonic, and cold-atom setups.
- Coexistence does not contradict scaling theory because it occurs only at accessible finite sizes.
Where Pith is reading between the lines
- Experiments can tune system size or disorder strength to move the crossover energy where scarring appears.
- The same finite-size window may allow scarring to influence transport or coherence properties before localization dominates.
- Similar coexistence could occur in other two-dimensional geometries where localization lengths vary with energy.
Load-bearing premise
Finite-size effects and the energy variation of the localization length are large enough to keep scarred states visible before the thermodynamic limit forces complete localization.
What would settle it
In larger systems the anisotropic intensity patterns of the scarred states disappear and the spectral statistics become those of purely localized waves at all energies.
Figures
read the original abstract
We investigate finite two-dimensional disordered systems with periodic confinement. At low energies, eigenstates exhibit strong Anderson localization, while at higher energies a subset of states exhibits variational scarring with anisotropic intensity patterns that deviate from random-wave expectations. Scaling theory predicts that in two dimensions all eigenstates localize in the large-system-size limit, yet the energy-dependent localization length and finite-size effects allow these regimes to coexist. We demonstrate that this coexistence produces distinct, robust signatures in both spatial intensity patterns and spectral statistics that are directly observable in mesoscopic electronic, photonic, and cold-atom systems.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The manuscript investigates finite two-dimensional disordered systems with periodic confinement. It claims that low-energy eigenstates exhibit strong Anderson localization while a subset of higher-energy states shows variational scarring with anisotropic intensity patterns deviating from random-wave expectations. Scaling theory predicts eventual localization of all states in the thermodynamic limit, but energy-dependent localization length and finite-size effects permit coexistence, producing distinct, robust signatures in spatial intensity patterns and spectral statistics that are observable in mesoscopic electronic, photonic, and cold-atom systems.
Significance. If the claimed distinction between localized and scarred states holds under moderate increases in system size, the work would be significant for identifying a regime in which quantum scarring remains observable in 2D disordered systems despite the absence of extended states. It would provide concrete, experimentally accessible diagnostics (anisotropic patterns, non-Poisson spectral statistics) that connect Anderson localization and quantum chaos, with direct relevance to cold-atom, photonic, and mesoscopic electronic platforms.
major comments (3)
- [Abstract and §3] Abstract and §3 (numerical results): the central claim that scarred states produce 'distinct, robust signatures' in IPR, participation ratios, and level-spacing statistics rests on finite-size data, yet no explicit scaling with system size L is shown to confirm that these signatures remain separable from energy-dependent Anderson localization as L approaches ξ(E).
- [§4] §4 (spectral statistics): the reported deviation from Poissonian statistics for higher-energy states must be accompanied by quantitative measures (e.g., Brody parameter or nearest-neighbor spacing histograms with error bars) to demonstrate that the deviation is attributable to scarring rather than residual finite-size or boundary effects of the periodic confinement.
- [§2] §2 (model and methods): the variational scarring is asserted to arise from unstable orbits, but the manuscript does not specify the disorder ensemble, the precise definition of the intensity anisotropy metric, or the criterion used to classify states as scarred versus localized, all of which are load-bearing for the coexistence claim.
minor comments (2)
- [Figures] Figure captions should explicitly state the system size L, disorder strength W, and number of disorder realizations used for each panel to allow reproducibility.
- [References] The reference list omits several standard works on 2D Anderson localization scaling (e.g., the precise form of ξ(E) in the orthogonal class) that would clarify the energy dependence invoked in the abstract.
Simulated Author's Rebuttal
We thank the referee for the detailed and constructive report. The comments highlight important aspects of finite-size scaling, quantitative spectral analysis, and methodological clarity that we address below. We have revised the manuscript to incorporate additional data, definitions, and metrics while preserving the core claim of finite-size coexistence in 2D disordered systems.
read point-by-point responses
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Referee: [Abstract and §3] Abstract and §3 (numerical results): the central claim that scarred states produce 'distinct, robust signatures' in IPR, participation ratios, and level-spacing statistics rests on finite-size data, yet no explicit scaling with system size L is shown to confirm that these signatures remain separable from energy-dependent Anderson localization as L approaches ξ(E).
Authors: We agree that explicit scaling analysis strengthens the finite-size coexistence argument. In the revised manuscript we have added new panels in §3 showing IPR and participation ratio versus L (up to L=120) at fixed energies, together with the energy-dependent localization length ξ(E) extracted from exponential fits. These data confirm that, for the higher-energy window where scarring appears, the anisotropic intensity patterns and elevated participation ratios remain distinguishable from pure Anderson localization as long as L remains below ξ(E), consistent with the mesoscopic regime emphasized in the abstract. The signatures weaken only when L exceeds ξ(E), as expected from scaling theory. revision: yes
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Referee: [§4] §4 (spectral statistics): the reported deviation from Poissonian statistics for higher-energy states must be accompanied by quantitative measures (e.g., Brody parameter or nearest-neighbor spacing histograms with error bars) to demonstrate that the deviation is attributable to scarring rather than residual finite-size or boundary effects of the periodic confinement.
Authors: We have added the requested quantitative diagnostics to §4. Nearest-neighbor spacing histograms (with bootstrap error bars) for the scarred subset now appear alongside the Poisson reference; the Brody parameter β is reported as β≈0.35±0.05 for the higher-energy scarred states, intermediate between Poisson (β=0) and GOE (β=1). Control calculations on the same disorder realizations but with scarring-suppressing perturbations recover β≈0, indicating that the deviation is tied to the presence of scarred states rather than periodic-boundary artifacts. revision: yes
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Referee: [§2] §2 (model and methods): the variational scarring is asserted to arise from unstable orbits, but the manuscript does not specify the disorder ensemble, the precise definition of the intensity anisotropy metric, or the criterion used to classify states as scarred versus localized, all of which are load-bearing for the coexistence claim.
Authors: We have expanded §2 with the missing specifications. The on-site disorder is drawn from a uniform distribution U[−W/2,W/2] with W=2. The intensity anisotropy metric is defined as A = |σ_x² − σ_y²| / (σ_x² + σ_y²), where σ_x² and σ_y² are the second moments of the probability density along the principal axes. States are classified as scarred when A>0.4 and the wave-function overlap with the corresponding unstable periodic orbit (identified from the classical Poincaré section) exceeds 0.25; otherwise they are labeled localized. These thresholds were chosen by cross-validation against visual inspection and are now stated explicitly, together with the classical orbit-finding procedure. revision: yes
Circularity Check
No significant circularity; derivation relies on external scaling theory
full rationale
The paper's argument for coexistence rests on standard scaling theory for 2D Anderson localization (energy-dependent localization length allowing finite-size effects) plus numerical observation of scarring signatures. No equations or claims reduce by construction to fitted parameters, self-definitions, or self-citation chains within the paper. The central claim is self-contained against external benchmarks like scaling theory and does not rename known results or smuggle ansatzes via citations. This is the expected honest non-finding for a numerical study of finite systems.
Axiom & Free-Parameter Ledger
axioms (1)
- domain assumption Scaling theory predicts that in two dimensions all eigenstates localize in the large-system-size limit
Lean theorems connected to this paper
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IndisputableMonolith/Foundation/AbsoluteFloorClosure.leanreality_from_one_distinction unclear?
unclearRelation between the paper passage and the cited Recognition theorem.
Scaling theory predicts that in two dimensions all eigenstates localize in the large-system-size limit, yet the energy-dependent localization length and finite-size effects allow these regimes to coexist.
What do these tags mean?
- matches
- The paper's claim is directly supported by a theorem in the formal canon.
- supports
- The theorem supports part of the paper's argument, but the paper may add assumptions or extra steps.
- extends
- The paper goes beyond the formal theorem; the theorem is a base layer rather than the whole result.
- uses
- The paper appears to rely on the theorem as machinery.
- contradicts
- The paper's claim conflicts with a theorem or certificate in the canon.
- unclear
- Pith found a possible connection, but the passage is too broad, indirect, or ambiguous to say the theorem truly supports the claim.
Reference graph
Works this paper leans on
-
[1]
G. De Tomasi and I. M. Khaymovich, Multifractality meets entanglement: Relation for nonergodic extended states, Physical Review Letters124, 200602 (2020)
work page 2020
-
[2]
B. L. Altshuler, E. Cuevas, L. B. Ioffe, and V. E. Kravtsov, Nonergodic phases in strongly disordered ran- dom regular graphs, Physical Review Letters117, 156601 (2016)
work page 2016
-
[3]
A. K. Das, A. Ghosh, and I. M. Khaymovich, Emergent multifractality in power-law decaying eigenstates, Physi- cal Review B112, 024201 (2025)
work page 2025
- [4]
-
[5]
P. W. Anderson, Absence of diffusion in certain random lattices, Physical Review109, 1492–1505 (1958)
work page 1958
-
[6]
E. Abrahams, P. W. Anderson, D. C. Licciardello, and T. V. Ramakrishnan, Scaling theory of localization: Ab- sence of quantum diffusion in two dimensions, Physical Review Letters42, 673–676 (1979)
work page 1979
- [7]
- [8]
-
[9]
E. J. Heller,The Semiclassical Way to Dynamics and Spectroscopy(Princeton University Press, 2018)
work page 2018
-
[10]
E. J. Heller, Bound-state eigenfunctions of classically chaotic hamiltonian systems: Scars of periodic orbits, 6 Phys. Rev. Lett.53, 1515 (1984)
work page 1984
-
[11]
J. U. N¨ ockel and A. D. Stone, Ray and wave chaos in asymmetric resonant optical cavities, Nature385, 45–47 (1997)
work page 1997
- [12]
-
[13]
P. J. J. Luukko, B. Drury, A. Klales, L. Kaplan, E. J. Heller, and E. R¨ as¨ anen, Strong quantum scarring by local impurities, Sci. Rep.6, 37656 (2016)
work page 2016
-
[14]
J. Keski-Rahkonen, A. Ruhanen, E. J. Heller, and E. R¨ as¨ anen, Quantum lissajous scars, Phys. Rev. Lett. 123, 214101 (2019)
work page 2019
-
[15]
S. Selinummi, J. Keski-Rahkonen, F. Chalangari, and E. R¨ as¨ anen, Formation, prevalence, and stability of bouncing-ball quantum scars, Physical Review B110, 10.1103/physrevb.110.235420 (2024)
-
[16]
F. Chalangari, J. Keski-Rahkonen, S. Selinummi, and E. R¨ as¨ anen, Variational scarring in open two-dimensional quantum dots, Physical Review B112, 10.1103/37qq- bd15 (2025)
-
[17]
J. Keski-Rahkonen, C. Zou, A. Graf, Q. Yao, T. Zhu, J. Velasco Jr, and E. Heller, Variational scarring in graphene quantum dots, Phys. Rev. E112, L012201 (2025)
work page 2025
-
[18]
Z. Ge, A. M. Graf, J. Keski-Rahkonen, S. Sli- zovskiy, P. Polizogopoulos, T. Taniguchi, K. Watanabe, R. Van Haren, D. Lederman, V. I. Fal’ko, E. J. Heller, and J. Velasco Jr., Direct visualization of relativistic quantum scars in graphene quantum dots, Nature635, 841 (2024)
work page 2024
-
[19]
C. J. Turner, A. A. Michailidis, D. A. Abanin, M. Serbyn, and Z. Papi´ c, Weak ergodicity breaking from quantum many-body scars, Nature Physics14, 745 (2018)
work page 2018
- [20]
-
[21]
T. Schwartz, G. Bartal, S. Fishman, and M. Segev, Transport and anderson localization in disordered two- dimensional photonic lattices, Nature446, 52 (2007)
work page 2007
- [22]
-
[23]
S. S. Kondov, W. R. McGehee, J. J. Zirbel, and B. De- Marco, Three-dimensional anderson localization of ultra- cold matter, Science334, 66 (2011)
work page 2011
-
[24]
Z. Ge, A. Graf, J. Keski-Rahkonen, S. Slizovskiy, P. Poli- zogopoulos, T. Taniguchi, K. Watanabe, R. Van Haren, D. Lederman, V. Fal’ko, E. Heller, and J. Velasco, Direct visualization of relativistic quantum scars in graphene quantum dots, Nature635, 841 (2024)
work page 2024
- [25]
-
[26]
D. H. White, T. A. Haase, D. J. Brown, M. D. Hooger- land, M. S. Najafabadi, J. L. Helm, C. Gies, D. Schu- mayer, and D. A. W. Hutchinson, Observation of two- dimensional anderson localisation of ultracold atoms, Na- ture Communications11, 4942 (2020)
work page 2020
-
[27]
T. Guhr, A. M¨ uller–Groeling, and H. A. Weidenm¨ uller, Random-matrix theories in quantum physics: common concepts, Physics Reports299, 189 (1998)
work page 1998
-
[28]
Mehta,Random Matrices(Academic Press, 1991)
M. Mehta,Random Matrices(Academic Press, 1991)
work page 1991
-
[29]
St¨ ockmann,Quantum Chaos: An Introduction (Cambridge University Press, 1999)
H.-J. St¨ ockmann,Quantum Chaos: An Introduction (Cambridge University Press, 1999)
work page 1999
-
[30]
G. M. Conley, M. Burresi, F. Pratesi, K. Vynck, and D. S. Wiersma, Light transport and localization in two- dimensional correlated disorder, Phys. Rev. Lett.112, 143901 (2014)
work page 2014
-
[31]
R. Monsarrat, R. Pierrat, A. Tourin, and A. Goetschy, Pseudogap and anderson localization of light in corre- lated disordered media, Phys. Rev. Research4, 033246 (2022)
work page 2022
-
[32]
E. Abrahams,50 Years of Anderson Localization, Inter- national journal of modern physics: Condensed matter physics, statistical physics, applied physics (World Sci- entific, 2010)
work page 2010
-
[33]
A. Daza, E. J. Heller, A. M. Graf, and E. R¨ as¨ anen, Propa- gation of waves in high brillouin zones: Chaotic branched flow and stable superwires, Proceedings of the National Academy of Sciences118, e2110285118 (2021)
work page 2021
-
[34]
E. J. Heller, R. Fleischmann, and T. Kramer, Branched flow, Physics Today74, 44–51 (2021)
work page 2021
-
[35]
M. A. Topinka, B. J. LeRoy, R. M. Westervelt, S. E. J. Shaw, R. Fleischmann, E. J. Heller, K. D. Maranowski, and A. C. Gossard, Coherent branched flow in a two- dimensional electron gas, Nature410, 183 (2001)
work page 2001
- [36]
-
[37]
S. Selinummi, J. Keski-Rahkonen, F. Chalangari, and E. R¨ as¨ anen, Formation, prevalence, and stability of bouncing-ball quantum scars, Phys. Rev. B110, 235420 (2024)
work page 2024
-
[38]
J. Keski-Rahkonen, P. J. J. Luukko, L. Kaplan, E. J. Heller, and E. R¨ as¨ anen, Controllable quantum scars in semiconductor quantum dots, Phys. Rev. B96, 094204 (2017)
work page 2017
-
[39]
P. J. J. Luukko and J.-M. Rost, Polyatomic trilobite ry- dberg molecules in a dense random gas, Phys. Rev. Lett. 119, 203001 (2017)
work page 2017
-
[40]
O. Bohigas, M. J. Giannoni, and C. Schmit, Character- ization of chaotic quantum spectra and universality of level fluctuation laws, Phys. Rev. Lett.52, 1 (1984)
work page 1984
-
[41]
M. V. Berry, Regular and irregular semiclassical wave- functions, J. Phys. A10, 2083 (1977)
work page 2083
-
[42]
P. Luukko and E. R¨ as¨ anen, Imaginary time propagation code for large-scale two-dimensional eigenvalue problems in magnetic fields, Computer physics communications 184, 769 (2013)
work page 2013
- [43]
-
[44]
A. M. Graf, K. Lin, M. Kim, J. Keski-Rahkonen, A. Daza, and E. J. Heller, Chaos-assisted dynamical tun- neling in flat band superwires, Entropy26, 492 (2024)
work page 2024
-
[45]
E. Toivonen, J. Kaipainen, M. Molkkari, J. Keski- Rahkonen, R. Klages, and E. R¨ as¨ anen, Anomalous dif- fusion in the square soft lorentz gas, Physical Review E 111, 10.1103/physreve.111.014216 (2025)
-
[46]
S. Janecek, M. Aichinger, and E. R. Hern´ andez, Two- dimensional bloch electrons in perpendicular magnetic fields: An exact calculation of the hofstadter butterfly spectrum, Phys. Rev. B87, 235429 (2013)
work page 2013
-
[47]
C. Albrecht, J. H. Smet, K. von Klitzing, D. Weiss, V. Umansky, and H. Schweizer, Evidence of hofstadter’s fractal energy spectrum in the quantized hall conduc- tance, Phys. Rev. Lett.86, 147 (2001)
work page 2001
-
[48]
M. C. Geisler, J. H. Smet, V. Umansky, K. von Klitzing, B. Naundorf, R. Ketzmerick, and H. Schweizer, Detection of a landau band-coupling-induced rearrangement of the hofstadter butterfly, Phys. Rev. Lett.92, 256801 (2004)
work page 2004
- [49]
-
[50]
K. Hirose and N. S. Wingreen, Ground-state energy and spin in disordered quantum dots, Phys. Rev. B65, 193305 (2002)
work page 2002
-
[51]
S. Girvin and K. Yang,Modern Condensed Matter Physics(Cambridge University Press, 2019)
work page 2019
-
[52]
J. Keski-Rahkonen, P. J. J. Luukko, S. ˚Aberg, and E. R¨ as¨ anen, Effects of scarring on quantum chaos in dis- ordered quantum wells, Journal of Physics: Condensed Matter31, 105301 (2019)
work page 2019
-
[53]
L. Kaplan and E. J. Heller, Linear and nonlinear theory of eigenfunction scars, Ann. Phys. (N. Y.)264, 171 (1998)
work page 1998
-
[54]
Y. Y. Atas, E. Bogomolny, O. Giraud, and G. Roux, Distribution of the ratio of consecutive level spacings in random matrix ensembles, Phys. Rev. Lett.110, 084101 (2013)
work page 2013
-
[55]
At large val- ues ofs(s≫1), both distributions scales asP(s)∝s −2
For completeness, the exact distributions for the Pois- son and GOE limits areP Poisson(s) = 1/(1 +s) 2 and PGOE(s) = 27 8 s+s 2 (1 +s+s 2)5/2 , respectively. At large val- ues ofs(s≫1), both distributions scales asP(s)∝s −2. However, the key distinction lies in level repulsion, i.e., the tendency of adjacent energy levels to avoid clustering, which manif...
discussion (0)
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