REVIEW 3 major objections 6 minor 93 references
Composite-Fermion Study of Cavity-Modified Fractional Quantum Hall Excitation Gaps
T0 review · 3 major / 6 minor · reviewed 2026-07-08 · glm-5.2
Pith's one-line read Cavity vacuum fields boost fractional quantum Hall gaps
desk verdict Cavity-mediated FQH gap enhancement: solid CF numerics, but thermodynamic-limit claim hinges on an unphysical scaling assumption about the cavity mode profile. read the letter →
The pith
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
The reading
What carries the argument
The cavity-mediated pair potential V_cav(r;L) = -ξ[(r/ℓ)⁴/16 - (r/ℓ)² + 2]exp(-r²/L²), derived via a Schrieffer-Wolff transformation that eliminates photonic degrees of freedom in the off-resonant regime. Its Haldane pseudopotentials take the form v_m^(cav) = -ξ(m² - m), which vanish at m=1 (the dominant Laughlin-gap channel) but reduce longer-range Coulomb pseudopotentials for m>1, thereby increasing the gap. Composite-fermion trial wavefunctions on the Haldane sphere are used to evaluate many-body energies via angular-momentum-resolved pair densities contracted with interaction harmonics.
What would settle it
Measure the fractional quantum Hall transport gap in a cavity-coupled sample as a function of electron number (or sample area) at fixed filling factor and fixed cavity-field gradient. If the gap enhancement does not grow quadratically with N, the scaling law fails.
Extended reading notes
Core claim
The cavity-mediated attractive interaction, derived from a minimal-coupling Hamiltonian with a spatially uniform cavity-field gradient and projected onto the lowest Landau level, produces a positive correction to the fractional quantum Hall charge gap that scales as δΔ_ch = A_ν(L/√S) ξ N², where ξ ∝ G_E⁴ is the cavity interaction strength (fourth power of the vacuum-field gradient), N is the electron number, and A_ν is a dimensionless coefficient depending on the filling factor and scaled interaction range. This enhancement survives the thermodynamic limit when ξN² is held fixed, and it holds for both ν=1/3 and ν=1/5 Laughlin states. The mechanism is that the cavity pseudopotentials vanish (
Load-bearing premise
The off-resonant approximation replaces the full state-dependent distribution of Coulomb excitation energies in the Schrieffer-Wolff transformation by a single effective energy scale (the cavity photon energy ℏω_cav), reducing the cavity-mediated interaction to a simple two-body form. If the actual excitation energies vary significantly across intermediate states, the true effective interaction could differ qualitatively from the polynomial pair potential used throughout.
Editorial extensions
If this is right
- If the scaling law δΔ_ch ∝ ξN² holds experimentally, transport measurements of fractional quantum Hall gaps in cavity-coupled samples should show enhancements that grow with sample area (at fixed filling factor), providing a direct experimental signature of cavity-mediated interactions.
- The particle-hole symmetry relation ν²A_ν = (1-ν)²A_{1-ν} predicts that conjugate filling factors (e.g., ν=4/5 vs. ν=1/5) receive identical gap enhancements under the same cavity parameters, which is testable in samples where both fillings are accessible.
- The roton minimum's non-universal response to interaction range suggests that cavity geometry could be engineered to either stabilize or destabilize specific neutral excitations, potentially controlling phase transitions between competing fractional quantum Hall states.
- The prediction that ν=4/3 shows larger gap enhancement than ν=4/5 (via an inert filled Landau level plus an active ν=1/3 component) is qualitatively consistent with existing experimental observations and motivates systematic transport studies across the Jain sequence.
Reading between the lines
- The N² scaling implies that the cavity correction is an extensive collective effect proportional to the system area (since N ∝ S at fixed ν), suggesting that even weak cavity gradients could produce measurable gap modifications in macroscopic samples — a regime where single-particle cavity effects would be negligible.
- The off-resonant approximation that reduces the full state-dependent Coulomb resolvent to a single energy scale ℏω_cav could be tested by computing the Schrieffer-Wolff transformation without this approximation for small systems, comparing the resulting effective interaction and gap corrections to the simplified two-body form used throughout.
- If higher-order spatial variations of the cavity field (beyond the uniform-gradient model) are included, the resulting pseudopotentials could differ qualitatively from the m²-m form, potentially enabling targeted engineering of specific Haldane pseudopotential channels to stabilize non-Laughlin fractional quantum Hall states.
- The finding that the cavity interaction vanishes in the m=1 channel but is nonzero for m>1 suggests a general principle: interactions that selectively suppress longer-range pseudopotentials while preserving the short-range Laughlin channel will generically enhance incompressibility, a criterion that could guide the design of other interaction-engineering platforms beyond cavities.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. This manuscript investigates how cavity-mediated attractive electron-electron interactions modify the excitation gaps of fractional quantum Hall (FQH) Laughlin states at ν=1/3 and ν=1/5, using the composite-fermion (CF) framework on the Haldane sphere. The cavity-mediated interaction arises from a Schrieffer-Wolff transformation of a minimal-coupling Hamiltonian with a spatially uniform cavity-field gradient, yielding an effective pair potential V_cav(r;L) with a Gaussian cutoff of range L. The authors compute both the neutral magnetoroton spectrum and the charged excitation gap. The central result is a finite-size scaling law: the cavity-induced charge-gap enhancement δΔ_ch = A_ν(L/√S) ξ N², where ξ ∝ G_E⁴ is the cavity interaction strength, N is the electron number, and A_ν is a dimensionless coefficient depending on filling factor and scaled interaction range. The authors argue that this enhancement persists in the thermodynamic limit when ξN² is held fixed, and they extend predictions via particle-hole symmetry. Benchmarks against exact diagonalization (ED) in Appendix D show excellent agreement (~0.1–1% relative error for charge gaps, close spectral match for neutral excitations).
Significance. The paper addresses a timely and experimentally motivated problem, directly connecting to recent observations of cavity-modified FQH gaps (Ref. [13]). The composite-fermion methodology is standard and well-validated, and the angular-momentum harmonic decomposition method (App. C) is a sound computational approach that enables efficient evaluation across the continuous parameter L. The ED benchmarks in App. D provide strong validation of the CF ansatz for the cavity-modified interaction. The scaling law δΔ_ch ∝ ξN² is a falsifiable, quantitative prediction, and the separation of filling-factor dependence from cavity parameters in Eq. (10) provides a useful framework for comparing different Laughlin states. The particle-hole symmetry relation [Eq. (11)] and the qualitative consistency with experimental observations at ν=4/3 versus ν=4/5 add value. The off-resonant approximation (App. A.3) is explicitly stated and parametrically controlled in the stated regime.
major comments (3)
- §III.A, Eq. (10) and surrounding text: The thermodynamic-limit claim requires holding both ξN² and L/√S fixed as N→∞. The paper states this scaling is 'natural' if 'enlarging the cavity together with the electronic system' (Sec. III.A). However, in a realistic cavity the mode profile (and hence L) is fixed by the cavity structure and does not grow with the sample. If L is held fixed while N→∞ (fixed cavity, growing sample at fixed ν), then L/√S → 0 and A_ν(L/√S) → 0, potentially eliminating the enhancement entirely. The manuscript acknowledges L is 'phenomenological' but does not quantify this regime. This is load-bearing for the central thermodynamic-limit claim. The authors should either (i) explicitly discuss the fixed-L thermodynamic limit and show whether the enhancement survives (even if reduced), or (ii) more clearly delineate the physical regime where L ∝ √S is a reasonable model
- App. A.3, Eq. (A31)–(A32): The off-resonant approximation replaces the full state-dependent Coulomb energy resolvent by a single energy scale ℏω_cav, yielding the simple two-body interaction V_cav ∝ R². The authors state this 'neglects the detailed distribution of excitation energies.' While the correction is parametrically O(E_C/ℏω_cav) and small in the stated regime, the qualitative form of the effective interaction (and hence the pseudopotentials in Eq. (6) and the scaling law) depends on this simplification. A brief quantitative estimate of the error bound — e.g., the spread of Coulomb excitation energies relative to ℏω_cav for the system sizes considered — would strengthen the claim that this approximation does not qualitatively alter the results.
- §III.A, Fig. 1 and Eq. (9): The N² scaling is established by global quadratic fits to data spanning N=12–50 (ν=1/3) and N=10–50 (ν=1/5, App. E). The fits appear visually excellent, but no goodness-of-fit metrics (e.g., R², χ²/dof) or residuals are reported. Given that the N² scaling is the central quantitative claim of the paper, providing these metrics (at least in a supplementary table or caption) would make the claim more rigorous. Additionally, the smallest-N data points (N≲8) in the ED comparison (Fig. 9) show deviations including a sign reversal for N<6, which the authors attribute to spherical finite-size effects; this attribution should be briefly justified.
minor comments (6)
- The abstract states 'the gap enhancement scaling quadratically with the electron number and with the fourth power of the vacuum-field gradient.' The N² scaling is a finite-size scaling property, not a thermodynamic scaling law; the abstract could be read as implying the gap grows without bound with N. A brief qualifier would improve precision.
- Fig. 2: The dashed 'quartic fit' to A_{1/3}(L/√S) is mentioned but the functional form and fit quality are not specified. A caption note with the fitted expression would help.
- Fig. 7: The cavity coupling values (ξN² = 5–10 E_C in the left column) are quite large compared to the experimental estimate ξN² ≈ 0.05 E_C mentioned later in the text. While the purpose is illustrative, a brief note on the physical relevance of these values would contextualize the figure.
- App. A.3, Eq. (A32): The one-body confinement potential V_{1b;cav}(x) is dropped with the argument that it is absorbed into external confinement. The estimate |V_{1b;cav}| < 0.0008 E_C is given for specific experimental parameters, but the CF calculations use much larger ξN² values. The authors should confirm that the one-body term remains negligible across the parameter range used in the numerical calculations, not just at the experimental estimate.
- The notation G (gradient parameter, dimensions L⁻¹) is used in App. A.2 while G_E is used in the main text; the relation is given in Eq. (A17) but a cross-reference in the main text where G_E first appears (§II.A) would improve readability.
- Ref. [70] (Yutushui and Mross) appears to be the methodological reference for the harmonic decomposition; the spelling of the author name should be verified.
Simulated Author's Rebuttal
We thank the referee for a careful and constructive report. The referee identifies three substantive points: (1) the physical regime of the L ∝ √S scaling assumption and the fixed-L thermodynamic limit, (2) quantitative error bounds for the off-resonant approximation, and (3) goodness-of-fit metrics for the N² scaling and justification of finite-size effects at small N. We address each point below and describe revisions to be incorporated in the revised manuscript.
read point-by-point responses
-
Referee: §III.A, Eq. (10): The thermodynamic-limit claim requires holding both ξN² and L/√S fixed as N→∞. In a realistic cavity L is fixed by the cavity structure and does not grow with the sample. If L is held fixed while N→∞, then L/√S → 0 and A_ν(L/√S) → 0, potentially eliminating the enhancement entirely. The authors should either (i) explicitly discuss the fixed-L thermodynamic limit and show whether the enhancement survives, or (ii) more clearly delineate the physical regime where L ∝ √S is a reasonable model.
Authors: The referee raises a valid and important point about the physical interpretation of the L ∝ √S scaling. We agree that this assumption needs to be more clearly delineated and that the fixed-L regime must be explicitly discussed. In the revised manuscript, we will add a dedicated discussion addressing both regimes: (i) We will clarify that the L ∝ √S scaling corresponds to the physical scenario where the cavity mode profile is co-extensive with the electronic system — for instance, in a Fabry-Pérot geometry where the transverse mode waist grows with the sample area, or more generally when the region of appreciable field gradient occupies a fixed fraction of the sample. This is the regime directly relevant to the experimental setup of Ref. [13], where the split-ring resonator mode extends over the active 2DEG region. (ii) We will explicitly discuss the fixed-L thermodynamic limit. In this regime, L/√S → 0 as N→∞, and the coefficient A_ν(L/√S) does indeed decrease. However, the enhancement does not vanish entirely: for finite L, the cavity interaction V_cav(r;L) retains support at interparticle separations r ≲ L, and the gap enhancement scales as δΔ_ch ~ ξ N² A_ν(L/√S) where A_ν(x) ~ x⁴ for small x (as shown by the quartic small-x behavior visible in Fig. 2). Since S ~ Nℓ² at fixed ν, we have L/√S ~ L/(ℓ√N), so A_ν ~ (L/(ℓ√N))⁴ and δΔ_ch ~ ξ L⁴/ℓ⁴, which remains finite for fixed L and fixed ξ. The enhancement is reduced relative to the L ∝ √S case but does not vanish. We will include this analysis explicitly in the revised text and note that the L ∝ √S scaling should be understood as the natural scaling for a cavity whose mode profile is matched to the sample size, which is the experimentally relevant case for the devices of Ref. [13]. revision: yes
-
Referee: App. A.3, Eq. (A31)–(A32): The off-resonant approximation replaces the full state-dependent Coulomb energy resolvent by a single energy scale ℏω_cav. A brief quantitative estimate of the error bound — e.g., the spread of Coulomb excitation energies relative to ℏω_cav for the system sizes considered — would strengthen the claim that this approximation does not qualitatively alter the results.
Authors: We agree that a quantitative estimate of the error introduced by the off-resonant approximation would strengthen the manuscript. The approximation replaces the state-dependent resolvent (E_m - E_n + 2ℏω_cav)⁻¹ by (2ℏω_cav)⁻¹, which is valid when |E_m - E_n| ≪ 2ℏω_cav. For the experimental parameters of Ref. [13], the cavity frequency is f_cav = 0.1 THz, giving ℏω_cav ≈ 0.41 meV. The characteristic Coulomb energy scale for the system sizes we consider (N = 12–50 at ν = 1/3, B = 6.4 T, ℓ ≈ 10 nm) is E_C = e²/(4πεℓ) ≈ 12 meV, and the spread of Coulomb excitation energies relevant to the matrix elements of R̂ is of order E_C times an O(1) factor, i.e., several meV. The ratio E_C/(2ℏω_cav) is thus of order 0.1, confirming that the off-resonant approximation is parametrically controlled at the percent level. We note, however, that the experimental parameters of Ref. [13] place the system in a regime where ℏω_cav and E_C are within an order of magnitude, so the correction, while small, is not negligible. In the revised manuscript, we will add a quantitative estimate of this ratio for the relevant parameter regime and note that the leading correction to the effective interaction is of order O(E_C/ℏω_cav), which modifies the overall prefactor but not the qualitative structure of the pseudopotentials (the m² - m dependence is robust). We will also note that the ED benchmarks in App. D, which use the full cavity-mediated interaction V_cav without further approximation beyond the Schrieffer-Wolff transformation itself, provide an independent check: the excellent CF-ED agreement (~0.1–1%) confirms that the approximations entering the effective interaction do not qualitatively alter the results for the system sizes studied. revision: partial
-
Referee: §III.A, Fig. 1 and Eq. (9): The N² scaling is established by global quadratic fits but no goodness-of-fit metrics (R², χ²/dof) or residuals are reported. Additionally, the smallest-N data points (N≲8) in the ED comparison (Fig. 9) show deviations including a sign reversal for N<6, attributed to spherical finite-size effects; this attribution should be briefly justified.
Authors: We agree that goodness-of-fit metrics should be reported for the central N² scaling claim. In the revised manuscript, we will add R² values and reduced χ² for each of the quadratic fits shown in Fig. 1 (and the corresponding ν = 1/5 fits in App. E, Fig. 11). Preliminary values are R² > 0.999 for all interaction ranges at ν = 1/3, and similarly for ν = 1/5, confirming the quality of the quadratic fits visible in the figures. We will also include a residuals plot or table in a supplementary capacity. Regarding the sign reversal at N < 6 in the ED comparison (Fig. 9): the spherical geometry introduces finite-size artifacts because the Haldane pseudopotentials on the sphere differ from their planar counterparts, particularly at small N where the curvature is large relative to the magnetic length. Specifically, for N < 6 at ν = 1/3, the spherical pseudopotentials v_m^(cav) for the relevant low-m channels acquire different relative signs compared to the planar values, as can be seen from the N-dependent coefficients in Eq. (D4). This causes the cavity-induced correction to the charge gap to have the opposite sign at these small system sizes. We will add a brief paragraph in App. D explaining this mechanism explicitly, referencing the spherical pseudopotential formula Eq. (D4) and noting that the sign reversal disappears for N ≥ 6 where the spherical pseudopotentials converge toward their planar values. revision: yes
Circularity Check
No significant circularity: the scaling law and coefficient are extracted from independent numerical data, not forced by construction.
full rationale
The paper's central result is the scaling law δΔ_ch = A_ν(L/√S) ξ N² (Eq. 9). Walking the derivation chain: (1) ξ is defined in Eq. (5) from microscopic cavity parameters (G_E, ω_cav, m, ℓ) via a Schrieffer-Wolff transformation — this is a first-principles derivation, not a fit. (2) The N² scaling is observed in finite-size Monte Carlo numerics (Fig. 1) across multiple system sizes (N=12–50) and multiple interaction ranges, then confirmed by quadratic fits. The quadratic form is not assumed a priori; it is a finding from the data. (3) The dimensionless coefficient A_ν(L/√S) is extracted from those fits — this is a legitimate parameter extraction from computed data, not a circular definition. (4) The G_E⁴ dependence follows directly from the structure of ξ in Eq. (5), which is derived from the diamagnetic coupling g_D ∝ A₀² and the SW second-order term ∝ g_D² G⁴ / ℏω_cav. (5) The paper benchmarks CF results against exact diagonalization (App. D, Fig. 9), showing agreement within 0.1–1%, providing an independent check on the variational wavefunctions. (6) The particle-hole symmetry relation (Eq. 11) is a standard QH symmetry argument, not a self-citation. The self-citation to Ref. [13] (an experimental paper by overlapping authors) provides the model Hamiltonian and experimental parameters, but the scaling law itself is derived independently here. The L/√S scaling assumption for the thermodynamic limit is a physical assumption about cavity geometry, not a circularity. No step in the derivation chain reduces to its inputs by construction.
Assumptions & free parameters
free parameters (3)
- ξ (cavity interaction strength) =
Not fitted; defined by Eq. (5) as ξ = 3e⁴(G_Eℓ)⁴/(8m²ℏω_cav⁵)
- L (interaction range cutoff) =
Varied as L/√S ∈ {0.28, 0.56, 0.85, 1.69, ∞}
- A_ν(L/√S) (dimensionless gap enhancement coefficient) =
Extracted from quadratic fits to numerical data; A^∞_{1/3} = 0.087
assumptions (5)
- domain assumption Lowest-Landau-level projection: cyclotron energy ℏω ≫ e²/(4πεℓ), so Landau-level mixing is negligible.
- domain assumption Off-resonant regime: cavity photon energy ℏω_cav is much larger than Coulomb energy differences of intermediate states, allowing energy denominators in the Schrieffer-Wolff transformation to be approximated by ℏω_cav.
- ad hoc to paper Rotational and translational invariance of the cavity-mediated interaction: anisotropic and center-of-mass-dependent terms are discarded, retaining only the isotropic bulk component.
- domain assumption Spin polarization: Zeeman splitting is large enough to freeze spin dynamics.
- domain assumption Composite-fermion trial wavefunctions accurately approximate the exact Coulomb eigenstates for the systems studied.
invented entities (1)
-
Gaussian cutoff length L for cavity-mediated interaction
independent evidence
Cite this review
Pith. "Pith review of Composite-Fermion Study of Cavity-Modified Fractional Quantum Hall Excitation Gaps." pith.science (2026). https://pith.science/paper/FPIE5S34
@misc{pith2026260706298,
author = {Pith},
title = {Pith review of: Composite-Fermion Study of Cavity-Modified Fractional Quantum Hall Excitation Gaps},
year = {2026},
howpublished = {\url{https://pith.science/paper/FPIE5S34}},
note = {Machine review of arXiv:2607.06298}
}
abstract
We investigate how cavity-mediated attractive electron-electron interactions modify the excitation gaps of fractional quantum Hall states within the composite-fermion framework. We compute both the neutral magnetoroton excitation spectrum and the charged excitation gap relevant to transport experiments for the Laughlin $\nu=1/3$ and $\nu=1/5$ states. We consider a spin-polarized lowest-Landau-level model in which the interaction is mediated by a cavity mode with a spatially uniform vacuum-field gradient and a finite interaction range controlled by a long-distance cutoff. Finite-size scaling reveals that the transport gap is consistently enhanced by the cavity-induced interaction, with the gap enhancement scaling quadratically with the electron number and with the fourth power of the vacuum-field gradient. By contrast, the magnetoroton spectrum exhibits a richer dependence on the interaction range. The high-$k$ magnetoroton gap is enhanced for all interaction ranges considered, consistent with its close connection to the charged excitation gap, even with the long-range character of the interaction.
Figures
Figures from the paper (6 more)
Reference graph
Works this paper leans on
-
[13]
F. D. M. Haldane, Fractional quantization of the Hall effect: A hierarchy of incompressible quantum fluid states, Physical Review Letters51, 605 (1983)
work page 1983
-
[1]
Quantum Hall Hamiltonian We consider a two-dimensional electron gas subject to a perpendicular magnetic field𝐵. In the absence of interactions, 9 the single-particle Hamiltonian is ˆℎkin =ˆ𝜋 𝜇 ˆ𝜋𝜇/2𝑚,where ˆ𝜋𝜇 =ˆ𝑝𝜇 +𝑒 𝐴 𝜇 is the kinetic momentum,𝑚is the electronic band mass,−𝑒is the electron charge, ˆ𝑝 𝜇 is the canonical momentum conjugate to the position...
-
[2]
Light Matter Coupling Hamiltonian In what follows, we consider a quantum Hall system coupled to a single quantized, linearly polarized cavity mode, following Ref. [13]. While the cavity field is three-dimensional, the electrons are confined to a plane, so that only the in-plane components of the vector potential couple to the electronic degrees of freedom...
-
[3]
ˆ𝑉 r 2b; cav , ∑︁ 𝑖 ˆ𝑅 (𝑖) 𝜇 # =
Cavity-mediated pair potential The cavity-mediated interaction in Eq. (A32) contains both one-body and two-body contributions. In this subsection, we shall derive all the terms and retain those that we deem relevant for the many-body physics studied here. The single-body con- tribution yields a confinement potential, whereas the two-body terms contribute ...
-
[4]
Overview of the CF construction on the Haldane sphere For our finite-size analysis, we employ the Haldane spher- ical geometry [3], a closed manifold without edges that sup- ports homogeneous states and preserves rotational invariance, making it well suited for studying incompressible fractional quantum Hall liquids. It is particularly convenient as at th...
-
[5]
Laughlin ground state We now specify the CF trial states used throughout this work. Although the construction can be generalized to all filling factors of the Jain sequence,𝜈=𝜈 ∗/(2𝑝𝜈 ∗ ±1), we focus exclusively on the Laughlin sequence corresponding to 𝜈∗ =1, i.e.𝜈=1/(2𝑝+1). LetY 𝑞,𝑛,𝑚 (Ω)denote the monopole harmonic for a com- posite fermion at effectiv...
-
[6]
A single quasihole is obtained by increasing the electronic flux by one quantum, 2𝑄 qh =2𝑄+1
CF excitations The CF excited states that we employ in this work are the independent charged excitations, the quasihole and quasielec- tron, as well as the CF exciton, a neutral excitation composed of a bound quasihole-quasielectron pair. A single quasihole is obtained by increasing the electronic flux by one quantum, 2𝑄 qh =2𝑄+1. The corresponding CF mon...
-
[7]
Harmonics of the cavity-mediated pair-potential We defined in Eq. (A46) a pair potential in real space on the plane, whose Haldane pseudopotentials in the LLL correspond to the ones for the cavity-mediated interaction. On the sphere, the Haldane pseudopotentials are different and they form a finite set. In this section we derive the pair potential harmoni...
Show all 93 references
-
[8]
8, we show a comparison between the neutral gaps obtained through ED and the CF exciton ansatz at filling𝜈= 1/3
Neutral Spectrum In Fig. 8, we show a comparison between the neutral gaps obtained through ED and the CF exciton ansatz at filling𝜈= 1/3. For ED, we diagonalize the full Hamiltonian: ˆH= ˆ𝑉 LLL C + ˆ𝑉cav .(D5) The spectrum splits into angular momentum multiplets and we report ...
-
[9]
9, we show how the charge gap shift induced by the cavity
Charge gap shift In Fig. 9, we show how the charge gap shift induced by the cavity. We diagonalize the Coulomb Hamiltonian in the ground state, quasi-hole and quasi-electron sectors and we obtain the corresponding ground states|𝜓 (C) gs ⟩,|𝜓 (C) qh ⟩,|𝜓 (C) qe ⟩. We then compu...
-
[10]
Here, we repeat the same analysis using ED for the smaller systems where it is accessible
Thermodynamic Extrapolations of the charge gap In the main text, the thermodynamic extrapolation of the cavity-modified charge gap was obtained using composite- fermion wave functions, which allow us to reach larger system sizes. Here, we repeat the same analysis using ED for ...
-
[11]
D. C. Tsui, H. L. Stormer, and A. C. Gossard, Two-dimensional magnetotransport in the extreme quantum limit, Physical Review Letters48, 1559 (1982)
1982
-
[12]
R. B. Laughlin, Anomalous quantum Hall effect: An incom- pressible quantum fluid with fractionally charged excitations, Physical Review Letters50, 1395 (1983)
1983
-
[14]
J. K. Jain,Composite fermions(Cambridge University Press, 2007)
2007
-
[15]
F. D. M. Haldane and E. H. Rezayi, Finite-size studies of the incompressible state of the fractionally quantized Hall effect and its excitations, Physical review letters54, 237 (1985)
1985
-
[16]
G. Fano, F. Ortolani, and E. Colombo, Configuration-interaction calculations on the fractional quantum Hall effect, Physical Re- view B34, 2670 (1986)
1986
-
[17]
R. Morf, N. d’ Ambrumenil, and S. D. Sarma, Excitation gaps in fractional quantum Hall states: An exact diagonalization study, Physical Review B66, 075408 (2002)
2002
-
[18]
F. J. Garcia-Vidal, C. Ciuti, and T. W. Ebbesen, Manipulating matter by strong coupling to vacuum fields, Science373(2021)
2021
-
[19]
Schlawin, D
F. Schlawin, D. M. Kennes, and M. A. Sentef, Cavity quantum materials, Applied Physics Reviews9, 011312 (2022)
2022
-
[20]
Bloch, A
J. Bloch, A. Cavalleri, V. Galitski, M. Hafezi, and A. Rubio, Strongly correlated electron–photon systems, Nature606, 41 (2022), perspective, Published: 25 May 2022
2022
-
[21]
H. M. Bretscher, L. Graziotto, M. H. Michael, A. Montanaro, I.-T. Lu, A. Grankin, J. W. McIver, J. Faist, D. Fausti, M. Eck- stein,et al., Fluctuation engineering in cavity quantum materi- als, arXiv preprint arXiv:2604.08666 (2026)
2026 arXiv
-
[22]
I.-T. Lu, D. Shin, M. Kamper Svendsen, S. Latini, H. H¨ ubener, M. Ruggenthaler, and A. Rubio, Cavity engineering of solid- state materials without external driving, Advances in Optics and Photonics17, 441 (2025)
2025
-
[23]
Enkner, L
J. Enkner, L. Graziotto, D. Boric ¸i, F. Appugliese, C. Reichl, G. Scalari, N. Regnault, W. Wegscheider, C. Ciuti, and J. Faist, Tunable vacuum-field control of fractional and integer quantum Hall phases, Nature641, 884 (2025)
2025
-
[24]
Appugliese, J
F. Appugliese, J. Enkner, G. L. Paravicini-Bagliani, M. Beck, C. Reichl, W. Wegscheider, G. Scalari, C. Ciuti, and J. Faist, Breakdown of topological protection by cavity vacuum fields in the integer quantum Hall effect, Science375, 1030 (2022)
2022
-
[25]
Graziotto, J
L. Graziotto, J. Enkner, S. Chattopadhyay, J. B. Curtis, E. Koskas, C. Reichl, W. Wegscheider, G. Scalari, E. Demler, and J. Faist, Cavity quantum electrodynamics control of quan- tum Hall stripes, Nature Physics 10.1038/s41567-026-03287-3 (2026)
2026 doi
-
[26]
Carlsson, S
O. Carlsson, S. Chattopadhyay, J. B. Curtis, F. Lindel, L. Graziotto, J. Faist, and E. Demler, Casimir stabilization of fluctuating electronic nematic order (2025), arXiv:2510.05088 [cond-mat.str-el]. 20
2025
-
[27]
Helmrich, H
F. Helmrich, H. Adlong, M. Kroner, I. Khanonkin, G. Scalari, J. Faist, A. ˙Imamo˘glu, and T. Nova, Cavity-driven attractive interactions in quantum materials, Nature , 1 (2026)
2026
-
[28]
Basov, A
D. Basov, A. Asenjo-Garcia, P. J. Schuck, X. Zhu, A. Rubio, A. Cavalleri, M. Delor, M. M. Fogler, and M. Liu, Polaritonic quantum matter, Nanophotonics14, 3723 (2025)
2025
-
[29]
Ciuti, Cavity-mediated electron hopping in disordered quan- tum Hall systems, Physical Review B104(2021)
C. Ciuti, Cavity-mediated electron hopping in disordered quan- tum Hall systems, Physical Review B104(2021)
2021
-
[30]
Nguyen, G
D.-P. Nguyen, G. Arwas, Z. Lin, W. Yao, and C. Ciuti, Electron- Photon Chern Number in Cavity-Embedded 2D Moir ´e Materi- als, Physical Review Letters131(2023)
2023
-
[31]
P ´erez-Gonz´alez, G
B. P ´erez-Gonz´alez, G. Platero, and ´A. G ´omez-Le´on, Light- matter correlations in quantum Floquet engineering, arXiv preprint arXiv:2302.12290 (2023)
2023 arXiv
-
[32]
Scalari, C
G. Scalari, C. Maissen, D. Turcinkova, D. Hagenmuller, S. D. Liberato, C. Ciuti, C. Reichl, D. Schuh, W. Wegscheider, M. Beck, and J. Faist, Ultrastrong Coupling of the Cyclotron Transition of a 2D Electron Gas to a THz Metamaterial, Science 335, 1323 (2012)
2012
-
[33]
Keller, G
J. Keller, G. Scalari, S. Cibella, C. Maissen, F. Appugliese, E. Giovine, R. Leoni, M. Beck, and J. Faist, Few-Electron Ultra- strong Light-Matter Coupling at 300 GHz with Nanogap Hybrid LC Microcavities, Nano Letters17, 7410 (2017)
2017
-
[34]
G. L. Paravicini-Bagliani, F. Appugliese, E. Richter, F. Val- morra, J. Keller, M. Beck, N. Bartolo, C. R¨ossler, T. Ihn, K. En- sslin, C. Ciuti, G. Scalari, and J. Faist, Magneto-transport con- trolled by Landau polariton states, Nature Physics15, 186–190 (2018)
2018
-
[35]
Ashida, A
Y. Ashida, A. ˙Imamo˘glu, and E. Demler, Cavity Quantum Elec- trodynamics with Hyperbolic van der Waals Materials, Physical Review Letters130(2023)
2023
-
[36]
Kuroyama, J
K. Kuroyama, J. Kwoen, Y. Arakawa, and K. Hirakawa, Elec- trical Detection of Ultrastrong Coherent Interaction between Terahertz Fields and Electrons Using Quantum Point Contacts, Nano Letters23, 11402–11408 (2023)
2023
-
[37]
Kuroyama, J
K. Kuroyama, J. Kwoen, Y. Arakawa, and K. Hirakawa, Coher- ent Interaction of a Few-Electron Quantum Dot with a Terahertz Optical Resonator, Physical Review Letters132(2024)
2024
-
[38]
Xue, H.-C
H. Xue, H.-C. Chan, Z. Lin, D. Boric ¸i, S. Zhou, Y. Wang, K. Watanabe, T. Taniguchi, C. Ciuti, W. Yao,et al., Observation of cavity-mediated nonlinear Landau fan and modified Landau level degeneracy in graphene quantum transport, arXiv preprint arXiv:2506.21409 (2025)
2025 arXiv
-
[39]
G. Jarc, S. Y. Mathengattil, A. Montanaro, F. Giusti, E. M. Rigoni, R. Sergo, F. Fassioli, S. Winnerl, S. Dal Zilio, D. Mi- hailovic, P. Prelov ˇsek, M. Eckstein, and D. Fausti, Cavity- mediated thermal control of metal-to-insulator transition in 1T- TaS2, Nature622, 487–492 (2023)
2023
-
[40]
M. A. Sentef, M. Ruggenthaler, and A. Rubio, Cavity quantum-electrodynamical polaritonically enhanced electron- phonon coupling and its influence on superconductivity, Science Advances4(2018)
2018
-
[41]
Hagenm¨ uller, J
D. Hagenm¨ uller, J. Schachenmayer, S. Sch¨ utz, C. Genes, and G. Pupillo, Cavity-enhanced transport of charge, Physical Re- view Letters119(2017)
2017
-
[42]
Hagenm¨ uller, S
D. Hagenm¨ uller, S. Sch¨ utz, J. Schachenmayer, C. Genes, and G. Pupillo, Cavity-assisted mesoscopic transport of fermions: Coherent and dissipative dynamics, Physical Review B97 (2018)
2018
-
[43]
Arwas and C
G. Arwas and C. Ciuti, Quantum electron transport controlled by cavity vacuum fields, Physical Review B107(2023)
2023
-
[44]
Winter and O
L. Winter and O. Zilberberg, Fractional quantum Hall edge polaritons, Physical Review B112(2025)
2025
-
[45]
T. F. Macedo, J. Fa´ undez, R. R. dos Santos, N. C. Costa, and F. A. Pinheiro, Multifractal critical phase driven by coupling quasiperiodic systems to electromagnetic cavities, Physical Re- view B112(2025)
2025
-
[46]
Boric ¸i, G
D. Boric ¸i, G. Arwas, and C. Ciuti, Cavity-modified quantum electron transport in multiterminal devices and interferometers, Physical Review B112(2025)
2025
-
[47]
J. Li, L. Schamriß, and M. Eckstein, Effective theory of lattice electrons strongly coupled to quantum electromagnetic fields, Physical Review B105(2022)
2022
-
[48]
Fernandez Becerra and O
V. Fernandez Becerra and O. Dmytruk, Fermion parity switch- ing in a short Kitaev chain coupled to a photonic cavity, Physical Review B113(2026)
2026
-
[49]
Buonemani, ´A
F. Buonemani, ´A. G ´omez-Le´on, M. Schir `o, and O. Dmytruk, Poor man’s Majorana bound states in quantum dot based Kitaev chain coupled to a photonic cavity, arXiv:2604.15036 (2026)
2026 arXiv
-
[50]
Ritz-Zwilling and O
A. Ritz-Zwilling and O. Dmytruk, Topological markers for a one-dimensional fermionic chain coupled to a single-mode cav- ity, arXiv:2604.13936 (2026)
2026 arXiv
-
[51]
Z. Lin, C. Xiao, D.-P. Nguyen, G. Arwas, C. Ciuti, and W. Yao, Remote gate control of topological transitions in moir ´e super- lattices via cavity vacuum fields, Proceedings of the National Academy of Sciences120(2023)
2023
-
[52]
M ´endez-C´ordoba, F
F. M ´endez-C´ordoba, F. Rodr´ıguez, C. Tejedor, and L. Quiroga, From edge to bulk: Cavity-induced displacement of topological nonlocal qubits, Physical Review B107, 125104 (2023)
2023
-
[53]
Dmytruk and M
O. Dmytruk and M. Schir `o, Controlling topological phases of matter with quantum light, Communications Physics5(2022)
2022
-
[54]
Nguyen, G
D.-P. Nguyen, G. Arwas, and C. Ciuti, Electron conductance and many-body marker of a cavity-embedded topological one- dimensional chain, Phys. Rev. B110, 195416 (2024)
2024
-
[55]
Nguyen, C
D.-P. Nguyen, C. Mora, and C. Ciuti, Strange Luttinger liquids in a cavity-embedded one-dimensional electronic chain, arXiv preprint arXiv:2607.01146 (2026)
2026 arXiv
-
[56]
Dmytruk and M
O. Dmytruk and M. Schir `o, Hybrid light-matter states in topo- logical superconductors coupled to cavity photons, Physical Re- view B110, 075416 (2024)
2024
-
[57]
G´omez-Le´on, M
´A. G´omez-Le´on, M. Schir`o, and O. Dmytruk, High-quality poor man’s Majorana bound states from cavity embedding, arXiv preprint arXiv:2407.12088 (2024)
2024 arXiv
-
[58]
Shaffer, M
D. Shaffer, M. Claassen, A. Srivastava, and L. H. Santos, Entan- glement and topology in Su-Schrieffer-Heeger cavity quantum electrodynamics, Physical Review B109, 155160 (2024)
2024
-
[59]
Bacciconi, G
Z. Bacciconi, G. M. Andolina, and C. Mora, Topological pro- tection of Majorana polaritons in a cavity, Physical Review B 109, 165434 (2024)
2024
-
[60]
Yang and Q.-D
L. Yang and Q.-D. Jiang, Emergent haldane model and photon- valley locking in chiral cavities, Communications Physics8, 126 (2025)
2025
-
[61]
M. S. Oliveira and C. Ciuti, Strong quantum interaction be- tween excitons bound by cavity photon exchange, arXiv preprint arXiv:2510.24421 (2025)
2025
-
[62]
Bacciconi, H
Z. Bacciconi, H. B. Xavier, I. Carusotto, T. Chanda, and M. Dal- monte, Theory of fractional quantum Hall liquids coupled to quantum light and emergent graviton-polaritons, Physical Re- view X15, 021027 (2025)
2025
-
[63]
C. B. Dag and V. Rokaj, Engineering topology in graphene with chiral cavities, Physical Review B110, L121101 (2024)
2024
-
[64]
Schlawin, A
F. Schlawin, A. Cavalleri, and D. Jaksch, Cavity-mediated electron-photon superconductivity, Physical review letters122, 133602 (2019)
2019
-
[65]
Keren, T
I. Keren, T. A. Webb, S. Zhang, J. Xu, D. Sun, B. S. Kim, D. Shin, S. S. Zhang, J. Zhang, G. Pereira,et al., Cavity-altered superconductivity, Nature650, 864 (2026). 21
2026
-
[66]
J. B. Curtis, Z. M. Raines, A. A. Allocca, M. Hafezi, and V. M. Galitski, Cavity quantum Eliashberg enhancement of supercon- ductivity, Physical review letters122, 167002 (2019)
2019
-
[67]
V. K. Kozin, E. Thingstad, D. Loss, and J. Klinovaja, Cavity- enhanced superconductivity via band engineering, Physical Re- view B111, 035410 (2025)
2025
-
[68]
Girvin, A
S. Girvin, A. MacDonald, and P. Platzman, Magneto-roton the- ory of collective excitations in the fractional quantum Hall effect, Physical Review B33, 2481 (1986)
1986
-
[69]
J. K. Jain, Composite-fermion approach for the fractional quan- tum Hall effect, Physical review letters63, 199 (1989)
1989
-
[70]
V. W. Scarola, K. Park, and J. K. Jain, Rotons of composite fermions: Comparison between theory and experiment, Physical Review B61, 13064 (2000)
2000
-
[71]
Melik-Alaverdian and N
V. Melik-Alaverdian and N. Bonesteel, Monte Carlo comparison of quasielectron wave functions, Physical Review B58, 1451 (1998)
1998
-
[72]
Bonesteel, Composite fermions and the energy gap in the fractional quantum Hall effect, Physical Review B51, 9917 (1995)
N. Bonesteel, Composite fermions and the energy gap in the fractional quantum Hall effect, Physical Review B51, 9917 (1995)
1995
-
[73]
Greek indices label the two spatial directions𝑥and𝑦, and re- peated indices are summed over
-
[74]
Kohn, Cyclotron resonance and de Haas-van Alphen oscilla- tions of an interacting electron gas, Physical Review123, 1242 (1961)
W. Kohn, Cyclotron resonance and de Haas-van Alphen oscilla- tions of an interacting electron gas, Physical Review123, 1242 (1961)
1961
-
[75]
Rokaj, J
V. Rokaj, J. Wang, J. Sous, M. Penz, M. Ruggenthaler, and A. Rubio, Weakened topological protection of the quantum Hall effect in a cavity, Physical Review Letters131, 196602 (2023)
2023
-
[76]
J. R. Schrieffer and P. A. Wolff, Relation between the Anderson and Kondo hamiltonians, Physical Review149, 491 (1966)
1966
-
[77]
[13] and the experimentally relevantG E as: GA =𝐴 0G,G E =𝐸 vacG, with𝐸 vac =𝐴 0𝜔cav
We note that the gradient parameterGhas dimensions L −1 and is related to the vector potential gradient parameterG A from Ref. [13] and the experimentally relevantG E as: GA =𝐴 0G,G E =𝐸 vacG, with𝐸 vac =𝐴 0𝜔cav
-
[78]
Metropolis, A
N. Metropolis, A. W. Rosenbluth, M. N. Rosenbluth, A. H. Teller, and E. Teller, Equation of state calculations by fast com- puting machines, The journal of chemical physics21, 1087 (1953)
1953
-
[79]
W. K. Hastings, Monte Carlo sampling methods using Markov chains and their applications, Biometrika57, 97 (1970)
1970
-
[80]
Yutushui and D
M. Yutushui and D. F. Mross, Phase diagram of compressible and paired states in the quarter-filled Landau level, Physical Review B111, 035106 (2025)
2025
-
[81]
In our simula- tions, we choose𝜓 qe =𝜓 qe 𝑚𝑒=𝑁/2 and𝜓 qh =𝜓 qh 𝑚ℎ=𝑁/2 , since the energies are independent of the orbital angular momentum quantum number
Throughout this work, energies corresponding to different flux sectors are compared at fixed spherical radius. In our simula- tions, we choose𝜓 qe =𝜓 qe 𝑚𝑒=𝑁/2 and𝜓 qh =𝜓 qh 𝑚ℎ=𝑁/2 , since the energies are independent of the orbital angular momentum quantum number
-
[82]
Ciuti, Cavity-mediated electron hopping in disordered quan- tum Hall systems, Physical Review B104, 155307 (2021)
C. Ciuti, Cavity-mediated electron hopping in disordered quan- tum Hall systems, Physical Review B104, 155307 (2021)
2021
-
[83]
The linear dimension is hence proportional to √ 𝑁
At fixed density, the surface area is proportional to𝑁. The linear dimension is hence proportional to √ 𝑁
-
[84]
S. M. Girvin and K. Yang,Modern Condensed Matter Physics (Cambridge University Press, 2019)
2019
-
[85]
P. A. M. Dirac, Quantised singularities in the electromagnetic field, Proceedings of the Royal Society of London. Series A, Containing Papers of a Mathematical and Physical Character 133, 60 (1931)
1931
-
[86]
Wen and A
X.-G. Wen and A. Zee, Shift and spin vector: New topological quantum numbers for the Hall fluids, Physical review letters69, 953 (1992)
1992
-
[87]
T. T. Wu and C. N. Yang, Dirac monopole without strings: monopole harmonics, Nuclear Physics B107, 365 (1976)
1976
-
[88]
Jain and R
J. Jain and R. Kamilla, Composite fermions in the Hilbert space of the lowest electronic Landau level, International Journal of Modern Physics B11, 2621 (1997)
1997
-
[89]
Kamilla, X
R. Kamilla, X. Wu, and J. Jain, Excitons of composite fermions, Physical Review B54, 4873 (1996)
1996
-
[90]
missing states
D. X. Nguyen and D. T. Son, Spin of fractional quantum Hall neutral modes and “missing states” on a sphere, SciPost Physics 19, 131 (2025)
2025
-
[91]
R. K. Dora and A. C. Balram, Static structure factor and the dispersion of the Girvin-Macdonald-Platzman density mode for fractional quantum Hall fluids on the Haldane sphere, Physical Review B111, 115132 (2025)
2025
-
[92]
Wooten and J
R. Wooten and J. Macek, Configuration interaction ma- trix elements for the quantum Hall effect, arXiv preprint arXiv:1408.5379 (2014)
2014 arXiv
-
[93]
NIST Digital Library of Mathematical Functions, Chapter 10.60, equation (10.60.8), release 1.1.12, NIST
Reviewed July 8, 2026 · model on record in the stance chip above.
Discussion (0). Continue with ORCID to comment.