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Screening and effective RPA-like charge susceptibility in the extended Hubbard model

T0 review · 3 major / 4 minor · reviewed 2026-08-11 · deepseek-v4-flash

Pith's one-line read This paper claims that the charge susceptibility of the extended Hubbard model is described by an RPA-like formula built from the U'=0 polarization, and traces this to a cancellation that leaves the density fermion-boson coupling almost…

desk verdict A solid and genuinely useful extension of SBE fRG to nonlocal interactions, but the RPA-like claim for the charge susceptibility rests on an unverified premise about the U'-independence of the polarization. read the letter →

arxiv 2412.07323 v1 pith:6J6CIQDQ submitted 2024-12-10 cond-mat.str-el

classification cond-mat.str-el
keywords extendedHubbardmodelsingle-bosonexchangefunctionalrenormalizationgroupchargesusceptibilityrandomphaseapproximationfermion-bosoncouplingfluctuationdiagnosticscharge-densitywave
verification ladder T0 review T1 audit T2 compute T3 formal

The pith

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The reading

The paper generalizes the single-boson exchange (SBE) decomposition of the two-particle vertex to nonlocal interactions and applies it in a functional renormalization group (fRG) calculation of the two-dimensional extended Hubbard model. Its central claim is that the charge (density) susceptibility is controlled by an RPA-like formula, $\chi^D \approx P^D_{U'=0}/(1+P^D_{U'=0}B^D)$, where $P^D$ is the polarization obtained from the Hubbard model at $U'=0$ with all vertex corrections included, and $B^D$ is the bosonic part of the bare interaction containing $U$ and the nearest-neighbor $U'$. The reason is that the density fermion-boson coupling $\lambda^D$ is almost independent of $U'$, even while $\chi^D$ grows strongly with $U'$ and eventually diverges near $U'/U \approx 1/4$. A fluctuation diagnostics traces this constancy to a cancellation between magnetic and density/superconducting contributions to the renormalization of $\lambda^D$. The paper also establishes a numerically cheap scheme, using only an s-wave form factor and neglecting rest-function flow and non-trivial high-frequency asymptotics, that is accurate in the weak-to-moderate coupling regime.

What carries the argument

The argument rides on splitting the bare interaction in each physical channel into a bosonic part $B^X(q)$ and a fermionic part $F^X(k,k')$, so that the single-boson-exchange vertex keeps its factorized form $\nabla^X = \lambda^X w^X \lambda^X$: a fermion-boson vertex $\lambda^X$ on either side of a screened interaction or bosonic propagator $w^X$. For the density channel $B^D(q)=U+4U'(\cos q_x+\cos q_y)$, so the nonlocal interaction enters as the initial value of the bosonic propagator, while the momentum-dependent remainder $F^X$ stays in the irreducible part. The polarization $P^X=\sum \lambda^X \Pi^X$ then determines the screened interaction via $w^X=B^X/(1+B^XP^X)$, and if $\lambda^D$ does not move with $U'$, substituting the $U'=0$ polarization reproduces Eq. (45). The cancellation that freezes $\lambda^D$ is exposed by a fluctuation diagnostics that splits it into magnetic, density, and superconducting contributions, and a sign-based poor-man's matrix reproduces the pattern without full numerics. The paper further uses the SBE approximation, neglecting the flow of the multiboson rest function, and checks that this is accurate in the tested regime.

What would settle it

Run the same fRG calculation at stronger coupling and lower temperature (for example $U=4$, $\beta=20$, $U'$ near the density-wave boundary) while keeping the full rest-function flow and d-wave form factors, and compare $\chi^D$ with $P^D_{U'=0}/(1+P^D_{U'=0}B^D)$; if $\lambda^D$ shows a $U'$-dependence comparable to $\lambda^M$, or if the susceptibility departs from the RPA-like formula by more than the few percent seen at $U=2$, the central claim fails.

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Extended reading notes

Core claim

On the paper's own terms, the central discovery is Eq. (45): for the two-dimensional extended Hubbard model with onsite $U$ and nearest-neighbor $U'$, the charge susceptibility can be written as $\chi^D \approx P^D_{U'=0}/(1+P^D_{U'=0}B^D)$, where $B^D(q)=U+4U'(\cos q_x+\cos q_y)$ and $P^D$ is the polarization built from the density fermion-boson coupling and the fRG bubble. The point is that $P^D$ is evaluated at $U'=0$ but retains all vertex corrections of the Hubbard model, so the formula is RPA-like in its $U'$-dependence, not bare RPA. The near-independence of $\lambda^D$ from $U'$ means the nonlocal interaction enters the charge response only through the bosonic bare interaction, which is why $\chi^D$ grows linearly with $U'$ up to the charge-density-wave divergence near $U'/U \approx 1/4$. The paper traces this constancy to cancellations between the magnetic and the density plus superconducting contributions in the fluctuation diagnostics of $\lambda^D$, and verifies a simplified computation scheme that neglects rest-function flow and nonlocal form factors in the weak-to-moderate coupling regime.

Load-bearing premise

The load-bearing premise is that the density fermion-boson coupling $\lambda^D$ stays independent of $U'$; this is verified numerically only at $U=2$, $\beta=10$ for two fillings, and the paper itself notes that the neglected rest-function flow would modify the picture at stronger coupling.

Editorial extensions

If this is right

  • Given the $U'=0$ Hubbard-model polarization, the charge response of the extended model at the tested parameters can be produced by the RPA-like denominator $1+P^D_{U'=0}B^D$ without recomputing the full $U'>0$ flow.
  • The linear growth of $\chi^D$ with $U'$ and its divergence near $U'/U \approx 1/4$ follow directly from the bosonic bare interaction $B^D$, not from interaction-induced vertex renormalization.
  • The simplified scheme with only an s-wave form factor, no rest-function flow, and no non-trivial high-frequency asymptotics reproduces susceptibilities and couplings within about two percent of the full calculation down to $T=0.1$, making parameter scans numerically feasible.
  • Magnetic and superconducting susceptibilities do not admit the same RPA-like description, because their fermion-boson couplings do depend on $U'$ through inter-channel feedback.
  • At stronger coupling or lower temperature the rest-function flow can no longer be neglected, so the RPA-like formula is a weak-to-moderate-coupling statement rather than a general identity.

Reading between the lines

Editorial extensions of the paper, not claims the author makes directly.

  • Going beyond the paper, Eq. (45) offers a cheap interpolation strategy: freeze the Hubbard-model polarization and vary only $B^D$ when scanning $U'$, provided the cancellation in $\lambda^D$ persists away from half filling and at lower temperature.
  • The sign-based diagnostic suggests the effect is structural rather than accidental; if so, longer-range nonlocal interactions that enter only through a bosonic density channel would also leave $\lambda^D$ nearly inert, which is testable in the same fRG setup.
  • Because $P^D_{U'=0}$ already contains Hubbard vertex corrections, bare-RPA estimates that ignore those corrections will overestimate the charge-density-wave tendency; the paper shows only the dependence on $U'$ is RPA-like, not the absolute value.
  • The same cancellation logic may carry over to retarded interactions such as phonon-mediated ones, where only the bosonic propagator changes while the density vertex stays close to its Hubbard value; the paper lists the Hubbard-Holstein model as a natural next application.
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Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, and a circularity audit.

Referee Report

3 major / 4 minor

Summary. The manuscript generalizes the single-boson exchange (SBE) formulation of the functional renormalization group to the extended Hubbard model with a nearest-neighbor interaction U'. The central methodological step is a modified notion of bare-interaction reducibility, splitting the bare interaction into a bosonic part B^X(q) and a fermionic part F^X(k,k'), which preserves the multiplicative form of the single-boson exchange while avoiding the numerically costly form-factor sums of a naive extension. The authors then establish a simplified computational scheme that keeps only an s-wave form factor, neglects the flow of the rest function, and omits non-trivial high-frequency asymptotics, and they test this scheme against fuller calculations at half filling and at van Hove filling for U=2. Their main physical claim is that, although the charge susceptibility chi^D is strongly enhanced by U' and eventually diverges near 4U'=U, the density fermion-boson coupling lambda^D is almost independent of U'. From this they conclude, via Eq. (45), that chi^D is approximately RPA-like with respect to the polarization of the U'=0 Hubbard model, and they trace the insensitivity of lambda^D to a cancellation between magnetic, density, and superconducting fluctuation channels using fluctuation diagnostics and a sign-based argument.

Significance. The methodological contribution is potentially valuable: a B-reducibility-based SBE scheme that retains the computational advantages of the local SBE formalism while accommodating nonlocal interactions. The conceptual claim, Eq. (45), is also significant if it survives scrutiny: it states that the nonlocal interaction enters the charge response only at the level of an RPA denominator, while all vertex corrections are encoded in a U'-independent polarization. This is a falsifiable and physically transparent prediction, and the authors are careful to distinguish it from bare RPA by noting that P^D contains vertex corrections. The paper reports systematic tests of several approximations (mixed bubbles, form-factor truncation, rest-function flow, high-frequency asymptotics) and includes fluctuation diagnostics with 2-loop corrections, with no fitted parameters. These are real strengths. However, the quantitative evidence for Eq. (45) is currently thinner than the narrative suggests: the U'-independence is demonstrated for lambda^D at a single value U=2, and the step from lambda^D independence to polarization independence is asserted rather than verified.

major comments (3)
  1. [§4.2, Eqs. (35) and (45)] The statement in §4.2 that the U'-independence of lambda^D 'translates to the polarization P^D' is not demonstrated. By Eq. (35), P^D is a sum over lambda^D times the bubble Π^D, and Π^D is built from fully renormalized propagators that acquire U'-dependence through the self-energy and through the chemical-potential shift introduced in §3.3 (Eqs. (25)-(27)); at finite U' the particle-hole symmetry is broken, so δμ changes with U'. Neither the U'-dependence of Σ nor that of Π^D is plotted or quantified. Since Eq. (45) is the central physical claim, I ask the authors to show P^D(Ω=0,q) directly as a function of U' (or at least the ratio P^D(U')/P^D(0)), and to compare the right-hand side of Eq. (45) with the numerically computed chi^D from the same fRG flow, reporting residuals as functions of U' and temperature.
  2. [§4.3, Figs. 14 and 15] The cancellation mechanism is argued for lambda^D, not for the polarization, and the numerical support is limited to a narrow parameter window. The 1-loop post-processed lambda^D in Fig. 14 shows a slight U'-dependence and only becomes approximately constant after adding 2-loop corrections in Fig. 15, while the susceptibilities used for Eq. (45) are obtained in the 1-loop scheme with the rest-function flow neglected; Fig. 6 documents a relative deviation of about 8% in chi^D at T=0.1 near the divergence. The sign-based diagnostic matrices in Eqs. (47)-(56) give only signs, not magnitudes, as the authors themselves note. Please state whether Eq. (45) is intended to hold at 1-loop or at the converged (multiloop) level, and test it directly in both cases rather than inferring it from lambda^D alone.
  3. [Abstract and §5] The abstract claims that the flow of the rest function can be neglected 'up to moderate interaction strengths', but the quantitative evidence is limited to U=2 at half filling and at one van Hove filling, with temperatures down to T=0.1. To make the scope claim load-bearing, the authors should either add a second interaction strength (e.g. U=4) or provide an analytic argument delimiting the regime in which the U'-independence of P^D and the neglect of the rest function remain valid. The qualitative sentence in §5 that at larger couplings and lower temperatures the rest function should be included currently defines the boundary only in words.
minor comments (4)
  1. [Fig. 14 caption] The caption says the superconducting (red) and density (green) contributions cancel the magnetic (red) one, but the color labeling appears inconsistent: the magnetic contribution should presumably not share the color 'red' with the superconducting one, and the density contribution is described as green.
  2. [Section 4.1] The text says the analysis in §4.1 uses beta=5 unless otherwise stated, while Fig. 5 is described as T=0.2; please make the notation between beta and T consistent in the captions and the text.
  3. [Throughout] There are several typographical and formatting issues, including 'F unding information' in the acknowledgments, 'na ¨ ıve' and 'responsible of'; a careful proofread would improve the presentation.
  4. [Eq. (55)] The derivation of Eq. (55) is compressed; since this sign rule plays a supporting role in the central cancellation argument, a short derivation or a reference to the diagrammatic enumeration in Fig. 16 would help the reader verify the signs without reverse-engineering them.

Circularity Check

0 steps flagged · score 0.0 of 10

No significant circularity: the RPA-like formula for the charge susceptibility rests on a numerical observation, not on a fit or a self-citation chain.

full rationale

The paper's central formula, Eq. (45), is an approximation built from the exact SBE relation w^D = B^D/(1+B^D P^D) (Eqs. (35)-(36)) together with the observed near-independence of the density fermion-boson coupling from U'. This is not a self-definitional reduction: P^D is not defined from χD, no parameter is fitted to the target susceptibility, and the formula is checked against the full fRG flow and against the independent RPA curves. The fragile inference that λD-independence implies P^D-independence, given that Π^D inherits U'-dependence through the self-energy and the chemical-potential shift, is a gap in evidence (flagged by the paper in footnote 4 and by the documented 1ℓ vs 2ℓ differences), but it is a correctness risk rather than a circular step. The extensive self-citation of the authors' own SBE-fRG framework is not load-bearing in a circular sense: the SBE decomposition is an exact diagrammatic reorganization, the flow equations are standard fRG equations, and the numerical conclusions are validated by internal comparison rather than by appeal to the cited papers. No equation in the derivation is equivalent to its input by construction.

Assumptions & free parameters 0 free parameters · 5 assumptions · 0 invented entities

The central claim relies on standard fRG truncation and on the SBE approximation (neglect of the rest function flow), both of which are tested only in a limited parameter window. No data fitting or invented entities are involved.

assumptions (5)
  • domain assumption The fRG flow is truncated at the two-particle vertex level (1ℓ, with 2ℓ corrections used in diagnostics).
    Standard for weak to moderate coupling; used throughout Section 3.3; the diagnostics post-processing assumes near-two-particle self-consistency (Section 3.4).
  • domain assumption The rest function flow M can be neglected (SBE approximation).
    Validated at U=2, T down to 0.1, at half filling and van Hove filling (Figs. 6 and 8), but stated to break down at larger couplings (Conclusions).
  • domain assumption Only s-wave form factor and diagonal bubbles are needed; mixed bubbles and nonlocal form factors are negligible.
    Tested in Figs. 5 and 7 at U=2, U'=U/4; the paper acknowledges that the approximation may not hold in other regimes (Section 4.1).
  • domain assumption The non-trivial high-frequency asymptotics of λ and M can be omitted.
    Verified in Appendix D (Fig. 19): corrections below 1% for the studied observables, though nonlocal λ components differ by up to 15% in relative terms.
  • ad hoc to paper The sign-based poor-man's fluctuation diagnostics (Eqs. 47-55) determines which channel contributions win.
    Introduced by the authors as heuristic, 'derived by heuristic arguments' in Section 4.3, to explain the cancellation in λD; it gives signs but not magnitudes.

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Cite this review

Pith. "Pith review of Screening and effective RPA-like charge susceptibility in the extended Hubbard model." pith.science (2026). https://pith.science/paper/6J6CIQDQ

@misc{pith2026241207323,
  author       = {Pith},
  title        = {Pith review of: Screening and effective RPA-like charge susceptibility in the extended Hubbard model},
  year         = {2026},
  howpublished = {\url{https://pith.science/paper/6J6CIQDQ}},
  note         = {Machine review of arXiv:2412.07323}
}
read the original abstract

We generalize the recently introduced single-boson exchange formalism to nonlocal interactions. In the functional renormalization group application to the extended Hubbard model in two dimensions, we show that the flow of the rest function can be neglected up to moderate interaction strengths. We explore the physics arising from the interplay between onsite and nearest-neighbor interactions in various parameter regimes by performing a fluctuation diagnostics. Differently from the magnetic and superconducting susceptibilities, the charge susceptibility appears to be described by the random phase approximation (RPA). We show that this behavior can be traced back to cancellations in the renormalization of the density fermion-boson coupling.

Figures

Figures reproduced from arXiv: 2412.07323 by the authors.

Figure 1
Figure 1. Diagrammatic representation of the parquet equation in the SBE for [PITH_FULL_IMAGE:figures/full_fig_p005_1.png] view at source ↗
Figure 2
Figure 2. Bare interaction of the extended Hubbard model in the different chan [PITH_FULL_IMAGE:figures/full_fig_p006_2.png] view at source ↗
Figure 3
Figure 3. Diagrammatic illustration of the bare interaction reducibility adapted [PITH_FULL_IMAGE:figures/full_fig_p007_3.png] view at source ↗
Figures from the paper (16 more)
Figure 4
Figure 4. Figure 4: The momentum grid with the refinement around ( [PITH_FULL_IMAGE:figures/full_fig_p011_4.png]
Figure 5
Figure 5. Figure 5: Bosonic propagator w X and (s-wave) fermion-boson coupling λ X as obtained from the calculation with and without mixed bubbles (left column) as well as with increasing number of form factors (right column), for U = 2, U ′ = U/4, T = 0.2, at half filling. 14 [PITH_FULL…
Figure 6
Figure 6. Figure 6: Momentum dependence of χ X and λ X as obtained from a calculation with and without the rest function, for the same parameters as in [PITH_FULL_IMAGE:figures/full_fig_p016_6.png]
Figure 7
Figure 7. Figure 7: Bosonic propagator w X and (s-wave) fermion-boson coupling λ X as obtained from the calculation with and without mixed bubbles (left column) as well as with increasing number of form factors (right column), for U = 2, U ′ = U/4, T = 0.2, at van Hove filling with t ′ = …
Figure 8
Figure 8. Figure 8: χ X and λ X as obtained from a calculation with and without the rest function, for the same parameters as in [PITH_FULL_IMAGE:figures/full_fig_p018_8.png]
Figure 9
Figure 9. Figure 9: Momentum dependence of χ X and λ X and their evolution with U ′ , for U = 2, β = 10, and at half filling (t ′ = 0). Note the logarithmic scale in the susceptibility panels for magnetic and density channels. 19 [PITH_FULL_IMAGE:figures/full_fig_p019_9.png]
Figure 10
Figure 10. Figure 10: Maximal values of the magnetic, charge (or density) and supercon [PITH_FULL_IMAGE:figures/full_fig_p020_10.png]
Figure 11
Figure 11. Figure 11: Competition between charge-density wave (left) and antiferromagnetic [PITH_FULL_IMAGE:figures/full_fig_p020_11.png]
Figure 12
Figure 12. Figure 12: Momentum dependence of λ X and χ X and their evolution with U ′ , for U = 2, β = 10, t ′ = −0.2, and at van Hove filling. Note the logarithmic scale in the susceptibility panels for magnetic and density channels. 21 [PITH_FULL_IMAGE:figures/full_fig_p021_12.png]
Figure 13
Figure 13. Figure 13: Maximal values of the magnetic, charge (or density) and supercon [PITH_FULL_IMAGE:figures/full_fig_p022_13.png]
Figure 14
Figure 14. Figure 14: Fluctuation diagnostics of λ D at half filling (left) and at finite doping (right), for the parameters of Figs. 9 and 12 (the dashed horizontal lines are guides to the eye). The contributions from the superconducting (red) and density (green) channels approximately ca…
Figure 15
Figure 15. Figure 15: Fluctuation diagnostics of λ D as in [PITH_FULL_IMAGE:figures/full_fig_p024_15.png]
Figure 16
Figure 16. Figure 16: a) Diagrammatic representation of ∇X′ = λ X′ w X′ λ X′ , and b)-c) lowest order contributions in U ′ . d) Contribution from ∇X′ to λ X ∼ R I XΠX, through a decomposition of I X ∼ P X′ R ∇X′ ΠX by Eq. (38), and e)-f) lowest order contributions in U ′ . Since the extend…
Figure 17
Figure 17. Figure 17: Diagrammatic illustration of the straightforward application of the [PITH_FULL_IMAGE:figures/full_fig_p029_17.png]
Figure 18
Figure 18. Figure 18: An example contribution to MSC of the extended Hubbard model which would does not decay to zero as ν, ν′ → ∞. ”vertical” momentum-dependent bare interaction will however contribute to diagrams of λ X and MX, leading to non-trivial frequency asymptotics. Consider for e…
Figure 19
Figure 19. Figure 19: Bosonic propagator w X and fermion-boson vertex λ X as obtained from the calculation with and without high-frequency asymptotics of λ asympt as well as with and without rest function asymptotics, for the same parameters as in [PITH_FULL_IMAGE:figures/full_fig_p033_19.png]

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Forward citations

Cited by 1 Pith paper

Reviewed papers in the Pith corpus that reference this work. Sorted by Pith novelty score. Full citation record

  1. Multiloop functional renormalization group from single bosons

    cond-mat.str-el 2025-12 conditional novelty 6.0 of 10

    A multiloop functional renormalization group in the single-boson-exchange representation reproduces parquet-approximation results for the 2D Hubbard model within a few percent when multi-boson rest functions are neglected.

Reference graph

Works this paper leans on

97 extracted references · 46 canonical work pages · cited by 1 Pith paper

  1. [1]

    Metzner, M

    W. Metzner, M. Salmhofer, C. Honerkamp, V. Meden and K. Sch¨ onhammer, Func- tional renormalization group approach to correlated fermion systems, Rev. Mod. Phys. 84, 299 (2012), doi:10.1103/RevModPhys.84.299

  2. [2]

    Dupuis, L

    N. Dupuis, L. Canet, A. Eichhorn, W. Metzner, J. Pawlowski, M. Tissier and N. Wschebor, The nonperturbative functional renormalization group and its appli- cations, Physics Reports 910, 1 (2021), doi:10.1016/j.physrep.2021.01.001

  3. [3]

    M. Qin, T. Sch¨ afer, S. Andergassen, P. Corboz and E. Gull, The hubbard model: A computational perspective, Annual Review of Condensed Matter Physics 13, 275 (2022), doi:10.1146/annurev-conmatphys-090921-033948

  4. [4]

    Tagliavini, C

    A. Tagliavini, C. Hille, F. B. Kugler, S. Andergassen, A. Toschi and C. Hon- erkamp, Multiloop functional renormalization group for the two-dimensional Hubbard model: Loop convergence of the response functions , SciPost Phys. 6, 009 (2019), doi:10.21468/SciPostPhys.6.1.009

  5. [5]

    Hille, F

    C. Hille, F. B. Kugler, C. J. Eckhardt, Y.-Y. He, A. Kauch, C. Honerkamp, A. Toschi and S. Andergassen, Quantitative functional renormalization group descrip- tion of the two-dimensional hubbard model , Phys. Rev. Research 2, 033372 (2020), doi:10.1103/PhysRevResearch.2.033372

  6. [6]

    A. A. Katanin, Fulfillment of ward identities in the functional renormalization group approach, Phys. Rev. B 70, 115109 (2004), doi:10.1103/PhysRevB.70.115109

  7. [7]

    F. B. Kugler and J. von Delft, Multiloop functional renormalization group that sums up all parquet diagrams , Phys. Rev. Lett. 120, 057403 (2018), doi:10.1103/PhysRevLett.120.057403

  8. [8]

    F. B. Kugler and J. von Delft, Multiloop functional renormalization group for general models, Phys. Rev. B 97, 35162 (2018), doi:10.1103/PhysRevB.97.035162

Show all 97 references
  1. [9]

    Metzner and D

    W. Metzner and D. Vollhardt, Correlated Lattice Fermions in d = ∞ Dimensions, Phys. Rev. Lett. 62, 324 (1989), doi:10.1103/PhysRevLett.62.324

  2. [10]

    Georges, G

    A. Georges, G. Kotliar, W. Krauth and M. J. Rozenberg, Dynamical mean-field theory of strongly correlated fermion systems and the limit of infinite dimensions , Rev. Mod. Phys. 68, 13 (1996), doi:10.1103/RevModPhys.68.13

  3. [11]

    Taranto, S

    C. Taranto, S. Andergassen, J. Bauer, K. Held, A. Katanin, W. Metzner, G. Rohringer and A. Toschi, From infinite to two dimensions through the functional renormalization group, Phys. Rev. Lett. 112, 196402 (2014), doi:10.1103/PhysRevLett.112.196402

  4. [12]

    Vilardi, C

    D. Vilardi, C. Taranto and W. Metzner, Antiferromagnetic and d-wave pairing correlations in the strongly interacting two-dimensional hubbard model from the functional renormalization group , Phys. Rev. B 99, 104501 (2019), doi:10.1103/PhysRevB.99.104501

  5. [13]

    P. M. Bonetti, A. Toschi, C. Hille, S. Andergassen and D. Vilardi, Single- boson exchange representation of the functional renormalization group for strongly interacting many-electron systems , Phys. Rev. Research 4, 013034 (2022), doi:10.1103/PhysRevResearch.4.013034. 34 SciP...

  6. [14]

    Husemann and M

    C. Husemann and M. Salmhofer, Efficient parametrization of the vertex function, Ω scheme, and the t, t ′ hubbard model at van hove filling , Phys. Rev. B 79, 195125 (2009), doi:10.1103/PhysRevB.79.195125

  7. [15]

    Vilardi, C

    D. Vilardi, C. Taranto and W. Metzner, Nonseparable frequency dependence of the two-particle vertex in interacting fermion systems , Phys. Rev. B 96, 235110 (2017), doi:10.1103/PhysRevB.96.235110

  8. [16]

    Rohringer, A

    G. Rohringer, A. Valli and A. Toschi, Local electronic correlation at the two-particle level, Phys. Rev. B 86, 125114 (2012), doi:10.1103/PhysRevB.86.125114

  9. [17]

    Wentzell, G

    N. Wentzell, G. Li, A. Tagliavini, C. Taranto, G. Rohringer, K. Held, A. Toschi and S. Andergassen, High-frequency asymptotics of the vertex function: Diagram- matic parametrization and algorithmic implementation , Phys. Rev. B 102 (2020), doi:10.1103/PhysRevB.102.085106

  10. [18]

    Wang, Y.-Y

    W.-S. Wang, Y.-Y. Xiang, Q.-H. Wang, F. Wang, F. Yang and D.-H. Lee, Functional renormalization group and variational monte carlo studies of the elec- tronic instabilities in graphene near 1 4 doping, Phys. Rev. B 85, 035414 (2012), doi:10.1103/PhysRevB.85.035414

  11. [19]

    Lichtenstein, D

    J. Lichtenstein, D. S´ anchez de la Pe˜ na, D. Rohe, E. Di Napoli, C. Hon- erkamp and S. Maier, High-performance functional Renormalization Group cal- culations for interacting fermions , Comput. Phys. Commun. 213, 100 (2017), doi:10.1016/j.cpc.2016.12.013

  12. [20]

    Heinzelmann, The single-boson exchange formalism and its application to the functional renormalization group , Ph.D

    S. Heinzelmann, The single-boson exchange formalism and its application to the functional renormalization group , Ph.D. thesis, Universit¨ at T¨ ubingen (2023)

  13. [21]

    Patricolo, M

    M. Patricolo, M. Gievers, K. Fraboulet, A. Al-Eryani, S. Heinzelmann, P. M. Bonetti, A. Toschi, D. Vilardi and S. Andergassen, Single-boson exchange formulation of the schwinger-dyson equation and its application to the functional renormalization group (2024), 2411.11661

  14. [22]

    R. A. Bari, Effects of short-range interactions on electron-charge ordering and lattice distortions in the localized state , Phys. Rev. B 3, 2662 (1971), doi:10.1103/PhysRevB.3.2662

  15. [23]

    Zhang and J

    Y. Zhang and J. Callaway, Extended hubbard model in two dimensions , Phys. Rev. B 39, 9397 (1989), doi:10.1103/PhysRevB.39.9397

  16. [24]

    Terletska, T

    H. Terletska, T. Chen and E. Gull, Charge ordering and correlation ef- fects in the extended hubbard model , Phys. Rev. B 95, 115149 (2017), doi:10.1103/PhysRevB.95.115149

  17. [25]

    Terletska, T

    H. Terletska, T. Chen, J. Paki and E. Gull, Charge ordering and nonlocal cor- relations in the doped extended hubbard model , Phys. Rev. B 97, 115117 (2018), doi:10.1103/PhysRevB.97.115117

  18. [26]

    J. Paki, H. Terletska, S. Iskakov and E. Gull, Charge order and antiferro- magnetism in the extended hubbard model , Phys. Rev. B 99, 245146 (2019), doi:10.1103/PhysRevB.99.245146

  19. [27]

    P. G. J. van Dongen, Extended hubbard model at weak coupling , Phys. Rev. B 50, 14016 (1994), doi:10.1103/PhysRevB.50.14016. 35 SciPost Physics Submission

  20. [28]

    P. G. J. van Dongen, Extended hubbard model at strong coupling , Phys. Rev. B 49, 7904 (1994), doi:10.1103/PhysRevB.49.7904

  21. [29]

    Wahle, N

    J. Wahle, N. Bl¨ umer, J. Schlipf, K. Held and D. Vollhardt, Microscopic con- ditions favoring itinerant ferromagnetism , Phys. Rev. B 58, 12749 (1998), doi:10.1103/PhysRevB.58.12749

  22. [30]

    Davoudi and A.-M

    B. Davoudi and A.-M. S. Tremblay, Non-perturbative treatment of charge and spin fluctuations in the two-dimensional extended hubbard model: Ex- tended two-particle self-consistent approach , Phys. Rev. B 76, 085115 (2007), doi:10.1103/PhysRevB.76.085115

  23. [31]

    Davoudi and A.-M

    B. Davoudi and A.-M. S. Tremblay, Nearest-neighbor repulsion and competing charge and spin order in the extended hubbard model , Phys. Rev. B 74, 035113 (2006), doi:10.1103/PhysRevB.74.035113

  24. [32]

    Si and J

    Q. Si and J. L. Smith, Kosterlitz-thouless transition and short range spatial correlations in an extended hubbard model , Phys. Rev. Lett. 77, 3391 (1996), doi:10.1103/PhysRevLett.77.3391

  25. [33]

    Medvedeva, S

    D. Medvedeva, S. Iskakov, F. Krien, V. V. Mazurenko and A. I. Lichtenstein, Exact diagonalization solver for extended dynamical mean-field theory , Phys. Rev. B 96, 235149 (2017), doi:10.1103/PhysRevB.96.235149

  26. [34]

    Jiang, U

    M. Jiang, U. R. H¨ ahner, T. C. Schulthess and T. A. Maier, d-wave superconductivity in the presence of nearest-neighbor coulomb repulsion , Phys. Rev. B 97, 184507 (2018), doi:10.1103/PhysRevB.97.184507

  27. [35]

    E. G. C. P. van Loon, A. I. Lichtenstein, M. I. Katsnelson, O. Parcollet and H. Hafermann, Beyond extended dynamical mean-field theory: Dual boson approach to the two-dimensional extended hubbard model , Phys. Rev. B 90, 235135 (2014), doi:10.1103/PhysRevB.90.235135

  28. [36]

    Rohringer, H

    G. Rohringer, H. Hafermann, A. Toschi, A. A. Katanin, A. E. Antipov, M. I. Katsnel- son, A. I. Lichtenstein, A. N. Rubtsov and K. Held, Diagrammatic routes to nonlocal correlations beyond dynamical mean field theory, Rev. Mod. Phys. 90, 025003 (2018), doi:10.1103/RevModPhys.90.025003

  29. [37]

    E. A. Stepanov, L. Peters, I. S. Krivenko, A. I. Lichtenstein, M. I. Katsnelson and A. N. Rubtsov, Quantum spin fluctuations and evolution of electronic structure in cuprates, npj Quant. Mater. 3, 54 (2018), doi:10.1038/s41535-018-0128-x

  30. [38]

    Pudleiner, A

    P. Pudleiner, A. Kauch, K. Held and G. Li, Competition between antiferromagnetic and charge density wave fluctuations in the extended hubbard model , Phys. Rev. B 100, 075108 (2019), doi:10.1103/PhysRevB.100.075108

  31. [39]

    Philoxene, V

    L. Philoxene, V. H. Dao and R. Fr´ esard, Spin and charge modulations of a half-filled extended hubbard model , Phys. Rev. B 106, 235131 (2022), doi:10.1103/PhysRevB.106.235131

  32. [40]

    Philoxene, V

    L. Philoxene, V. H. Dao and R. Fr´ esard, Phase coexistence in a half-filled extended hubbard model , Modern Physics Letters B 38(21), 2342002 (2024), doi:10.1142/S0217984923420022. 36 SciPost Physics Submission

  33. [41]

    Sushchyev and S

    A. Sushchyev and S. Wessel, Thermodynamics of the metal-insulator transition in the extended hubbard model from determinantal quantum monte carlo , Phys. Rev. B 106, 155121 (2022), doi:10.1103/PhysRevB.106.155121

  34. [42]

    S. a. d. A. Sousa-J´ unior, N. C. Costa and R. R. dos Santos,Half-filled extended hubbard model on a square lattice: Phase boundaries from determinant quantum monte carlo simulations, Phys. Rev. B 109, 165102 (2024), doi:10.1103/PhysRevB.109.165102

  35. [43]

    Sch¨ uler, M

    M. Sch¨ uler, M. R¨ osner, T. O. Wehling, A. I. Lichtenstein and M. I. Kat- snelson, Optimal hubbard models for materials with nonlocal coulomb interac- tions: Graphene, silicene, and benzene , Phys. Rev. Lett. 111, 036601 (2013), doi:10.1103/PhysRevLett.111.036601

  36. [44]

    Husemann and W

    C. Husemann and W. Metzner, Incommensurate nematic fluctuations in the two-dimensional hubbard model , Phys. Rev. B 86, 085113 (2012), doi:10.1103/PhysRevB.86.085113

  37. [45]

    F. Wu, T. Lovorn, E. Tutuc and A. H. MacDonald, Hubbard model physics in transition metal dichalcogenide moir´ e bands, Phys. Rev. Lett. 121, 026402 (2018), doi:10.1103/PhysRevLett.121.026402

  38. [46]

    Gneist, L

    N. Gneist, L. Classen and M. M. Scherer, Competing instabilities of the extended hubbard model on the triangular lattice: Truncated-unity functional renormaliza- tion group and application to moir´ e materials , Phys. Rev. B 106, 125141 (2022), doi:10.1103/PhysRevB.106.125141

  39. [47]

    Raghu, X.-L

    S. Raghu, X.-L. Qi, C. Honerkamp and S.-C. Zhang, Topological mott insulators , Phys. Rev. Lett. 100, 156401 (2008), doi:10.1103/PhysRevLett.100.156401

  40. [48]

    M. M. Scherer, S. Uebelacker and C. Honerkamp, Instabilities of interact- ing electrons on the honeycomb bilayer , Phys. Rev. B 85, 235408 (2012), doi:10.1103/PhysRevB.85.235408

  41. [49]

    M. M. Scherer, S. Uebelacker, D. D. Scherer and C. Honerkamp, Interact- ing electrons on trilayer honeycomb lattices , Phys. Rev. B 86, 155415 (2012), doi:10.1103/PhysRevB.86.155415

  42. [50]

    M. L. Kiesel, C. Platt and R. Thomale, Unconventional fermi surface insta- bilities in the kagome hubbard model , Phys. Rev. Lett. 110, 126405 (2013), doi:10.1103/PhysRevLett.110.126405

  43. [51]

    S. Wolf, D. Di Sante, T. Schwemmer, R. Thomale and S. Rachel, Triplet superconduc- tivity from nonlocal coulomb repulsion in an atomic sn layer deposited onto a si(111) substrate, Phys. Rev. Lett. 128, 167002 (2022), doi:10.1103/PhysRevLett.128.167002

  44. [52]

    Schwemmer, H

    T. Schwemmer, H. Hohmann, M. D¨ urrnagel, J. Potten, J. Beyer, S. Rachel, Y.- M. Wu, S. Raghu, T. M¨ uller, W. Hanke and R. Thomale, Sublattice modulated superconductivity in the kagome hubbard model , Phys. Rev. B 110, 024501 (2024), doi:10.1103/PhysRevB.110.024501

  45. [53]

    Krien, A

    F. Krien, A. Valli and M. Capone, Single-boson exchange decomposition of the vertex function, Phys. Rev. B 100, 155149 (2019), doi:10.1103/PhysRevB.100.155149. 37 SciPost Physics Submission

  46. [54]

    Fraboulet, S

    K. Fraboulet, S. Heinzelmann, P. M. Bonetti, A. Al-Eryani, D. Vilardi, A. Toschi and S. Andergassen, Single-boson exchange functional renormalization group application to the two-dimensional Hubbard model at weak coupling , Eur. Phys. J. B 95, 202 (2022), doi:10.1140/epjb/s100...

  47. [55]

    Sch¨ afer, G

    T. Sch¨ afer, G. Rohringer, O. Gunnarsson, S. Ciuchi, G. Sangiovanni and A. Toschi, Divergent Precursors of the Mott-Hubbard Transition at the Two-Particle Level, Phys. Rev. Lett. 110, 246405 (2013), doi:10.1103/PhysRevLett.110.246405

  48. [56]

    Janiˇ s and V

    V. Janiˇ s and V. Pokorn´ y,Critical metal-insulator transition and divergence in a two- particle irreducible vertex in disordered and interacting electron systems , Phys. Rev. B 90, 045143 (2014), doi:10.1103/PhysRevB.90.045143

  49. [57]

    Gunnarsson, T

    O. Gunnarsson, T. Sch¨ afer, J. P. F. LeBlanc, J. Merino, G. Sangiovanni, G. Rohringer and A. Toschi, Parquet decomposition calculations of the electronic self-energy, Phys. Rev. B 93, 245102 (2016), doi:10.1103/PhysRevB.93.245102

  50. [58]

    Sch¨ afer, A

    T. Sch¨ afer, A. Toschi and K. Held, Dynamical vertex approximation for the two-dimensional hubbard model , J. Magn. Magn. Mater. 400, 107 (2016), doi:10.1016/j.jmmm.2015.07.103

  51. [59]

    Ribic, G

    T. Ribic, G. Rohringer and K. Held, Nonlocal correlations and spectral properties of the Falicov-Kimball model , Phys. Rev. B 93, 195105 (2016), doi:10.1103/PhysRevB.93.195105

  52. [60]

    Gunnarsson, G

    O. Gunnarsson, G. Rohringer, T. Sch¨ afer, G. Sangiovanni and A. Toschi,Breakdown of Traditional Many-Body Theories for Correlated Electrons , Phys. Rev. Lett. 119, 056402 (2017), doi:10.1103/PhysRevLett.119.056402

  53. [61]

    Vuˇ ciˇ cevi´ c, N

    J. Vuˇ ciˇ cevi´ c, N. Wentzell, M. Ferrero and O. Parcollet,Practical consequences of the Luttinger-Ward functional multivaluedness for cluster DMFT methods , Phys. Rev. B 97, 125141 (2018), doi:10.1103/PhysRevB.97.125141

  54. [62]

    Chalupa, P

    P. Chalupa, P. Gunacker, T. Sch¨ afer, K. Held and A. Toschi, Divergences of the irreducible vertex functions in correlated metallic systems: Insights from the Anderson impurity model, Phys. Rev. B 97, 245136 (2018), doi:10.1103/PhysRevB.97.245136

  55. [63]

    Thunstr¨ om, O

    P. Thunstr¨ om, O. Gunnarsson, S. Ciuchi and G. Rohringer, Analytical investigation of singularities in two-particle irreducible vertex functions of the hubbard atom , Phys. Rev. B 98, 235107 (2018), doi:10.1103/PhysRevB.98.235107

  56. [64]

    Springer, P

    D. Springer, P. Chalupa, S. Ciuchi, G. Sangiovanni and A. Toschi, Interplay between local response and vertex divergences in many-fermion systems with on-site attraction, Phys. Rev. B 101, 155148 (2020), doi:10.1103/PhysRevB.101.155148

  57. [65]

    Melnick and G

    C. Melnick and G. Kotliar, Fermi-liquid theory and divergences of the two-particle irreducible vertex in the periodic anderson lattice , Phys. Rev. B 101, 165105 (2020), doi:10.1103/PhysRevB.101.165105

  58. [66]

    Reitner, P

    M. Reitner, P. Chalupa, L. Del Re, D. Springer, S. Ciuchi, G. Sangio- vanni and A. Toschi, Attractive effect of a strong electronic repulsion: The physics of vertex divergences , Phys. Rev. Lett. 125, 196403 (2020), doi:10.1103/PhysRevLett.125.196403. 38 SciPost Physics Submission

  59. [67]

    Chalupa, T

    P. Chalupa, T. Sch¨ afer, M. Reitner, D. Springer, S. Andergassen and A. Toschi,Fin- gerprints of the Local Moment Formation and its Kondo Screening in the Generalized Susceptibilities of Many-Electron Problems , Phys. Rev. Lett. 126, 056403 (2021), doi:10.1103/PhysRevLett.126.056403

  60. [68]

    T. B. Mazitov and A. A. Katanin, Effect of local magnetic moments on spectral properties and resistivity near interaction- and doping-induced mott transitions, Phys. Rev. B 106, 205148 (2022), doi:10.1103/PhysRevB.106.205148

  61. [69]

    M. Pelz, S. Adler, M. Reitner and A. Toschi, Highly nonperturbative nature of the mott metal-insulator transition: Two-particle vertex divergences in the coexistence region, Phys. Rev. B 108, 155101 (2023), doi:10.1103/PhysRevB.108.155101

  62. [70]

    N. E. Bickers, Self-Consistent Many-Body Theory for Condensed Matter Systems , In D. S´ en´ echal, A.-M. Tremblay and C. Bourbonnais, eds.,Theoretical Methods for Strongly Correlated Electrons, pp. 237–296. Springer New York, New York, NY, ISBN 978-0-387-21717-8, doi:10.1007/0...

  63. [71]

    Krien, A

    F. Krien, A. I. Lichtenstein and G. Rohringer, Fluctuation diagnostic of the nodal/antinodal dichotomy in the hubbard model at weak coupling: A parquet dual fermion approach, Phys. Rev. B 102 (2020), doi:10.1103/physrevb.102.235133

  64. [72]

    M. V. Sadovskii, Diagrammatics, World Scientific, 2nd edn., doi:10.1142/11605 (2019)

  65. [73]

    Bickers and D

    N. Bickers and D. Scalapino, Conserving approximations for strongly fluctuating electron systems. i. formalism and calculational approach , Annals of Physics 193, 206 (1989), doi:https://doi.org/10.1016/0003-4916(89)90359-X

  66. [74]

    D. J. Scalapino, A common thread: The pairing interaction for unconventional super- conductors, Rev. Mod. Phys. 84(4), 1383 (2012), doi:10.1103/RevModPhys.84.1383, 1207.4093

  67. [75]

    E. A. Stepanov, V. Harkov and A. I. Lichtenstein, Consistent partial bosoniza- tion of the extended hubbard model , Phys. Rev. B 100, 205115 (2019), doi:10.1103/PhysRevB.100.205115

  68. [76]

    Hedin, New method for calculating the one-particle green ’s function with application to the electron-gas problem , Phys

    L. Hedin, New method for calculating the one-particle green ’s function with application to the electron-gas problem , Phys. Rev. 139, A796 (1965), doi:10.1103/PhysRev.139.A796

  69. [77]

    E. G. C. P. van Loon, M. R¨ osner, M. I. Katsnelson and T. O. Wehling, Random phase approximation for gapped systems: Role of vertex corrections and applicability of the constrained random phase approximation , Phys. Rev. B 104, 045134 (2021), doi:10.1103/PhysRevB.104.045134

  70. [78]

    P. M. Bonetti, Accessing the ordered phase of correlated fermi systems: Vertex bosonization and mean-field theory within the functional renormalization group, Phys. Rev. B 102, 235160 (2020), doi:10.1103/PhysRevB.102.235160

  71. [79]

    Gunnarsson, T

    O. Gunnarsson, T. Sch¨ afer, J. P. F. LeBlanc, E. Gull, J. Merino, G. Sangio- vanni, G. Rohringer and A. Toschi, Fluctuation diagnostics of the electron self- energy: Origin of the pseudogap physics , Phys. Rev. Lett. 114, 236402 (2015), doi:10.1103/PhysRevLett.114.236402. 39 ...

  72. [81]

    Sch¨ afer and A

    T. Sch¨ afer and A. Toschi, How to read between the lines of electronic spectra: the diagnostics of fluctuations in strongly correlated electron systems , Journal of Physics: Condensed Matter 33, 214001 (2021), doi:10.1088/1361-648x/abeb44

  73. [82]

    Y. Yu, S. Iskakov, E. Gull, K. Held and F. Krien, Unambiguous fluctuation decom- position of the self-energy: Pseudogap physics beyond spin fluctuations , Phys. Rev. Lett. 132, 216501 (2024), doi:10.1103/PhysRevLett.132.216501

  74. [83]

    Heinzelmann, A

    S. Heinzelmann, A. Toschi and S. Andergassen, Entangled magnetic, charge, and su- perconducting pairing correlations in the two-dimensional hubbard model: a functional renormalization-group analysis (2023), 2308.06497

  75. [84]

    smok- ing gun

    S. Adler, F. Krien, P. Chalupa-Gantner, G. Sangiovanni and A. Toschi, Non-perturbative intertwining between spin and charge correlations: A “smok- ing gun ” single-boson-exchange result , SciPost Phys. 16, 054 (2024), doi:10.21468/SciPostPhys.16.2.054

  76. [85]

    Krien and A

    F. Krien and A. Valli, Parquetlike equations for the hedin three-leg vertex, Phys. Rev. B 100, 245147 (2019), doi:10.1103/PhysRevB.100.245147

  77. [86]

    Krien, A

    F. Krien, A. Kauch and K. Held, Tiling with triangles: parquet and gwγ methods unified, Phys. Rev. Res. 3, 013149 (2021), doi:10.1103/PhysRevResearch.3.013149

  78. [87]

    Gievers, E

    M. Gievers, E. Walter, A. Ge, J. von Delft and F. B. Kugler, Multiloop flow equations for single-boson exchange fRG , Eur. Phys. J. B 95, 108 (2022), doi:10.1140/epjb/s10051-022-00353-6

  79. [88]

    Fraboulet, A

    K. Fraboulet, A. Al-Eryani, S. Heinzelmann and S. Andergassen, Multiloop extension of the single-boson exchange functional renormalization group and application to the two-dimensional hubbard model (2024)

  80. [89]

    Hille, D

    C. Hille, D. Rohe, C. Honerkamp and S. Andergassen, Pseudogap opening in the two-dimensional hubbard model: A functional renormalization group analysis , Phys. Rev. Research 2 (2020), doi:10.1103/PhysRevResearch.2.033068

  81. [90]

    Braun, Functional renormalization group analysis of the pseudogap opening in the two-dimensional Hubbard model, Master’s thesis, Universit¨ at T¨ ubingen (2021)

    H. Braun, Functional renormalization group analysis of the pseudogap opening in the two-dimensional Hubbard model, Master’s thesis, Universit¨ at T¨ ubingen (2021)

  82. [91]

    Shinaoka, J

    H. Shinaoka, J. Otsuki, M. Ohzeki and K. Yoshimi, Compressing green ’s function us- ing intermediate representation between imaginary-time and real-frequency domains , Phys. Rev. B 96, 035147 (2017), doi:10.1103/PhysRevB.96.035147

  83. [92]

    Chikano, J

    N. Chikano, J. Otsuki and H. Shinaoka, Performance analysis of a physically con- structed orthogonal representation of imaginary-time green ’s function , Phys. Rev. B 98, 035104 (2018), doi:10.1103/PhysRevB.98.035104

  84. [93]

    J. Kaye, K. Chen and O. Parcollet, Discrete lehmann representation of imaginary time green ’s functions , Phys. Rev. B 105, 235115 (2022), doi:10.1103/PhysRevB.105.235115. 40 SciPost Physics Submission

  85. [94]

    J. Kaye, K. Chen and H. U. Strand, libdlr: Efficient imaginary time calculations using the discrete lehmann representation , Computer Physics Communications 280, 108458 (2022), doi:10.1016/j.cpc.2022.108458

  86. [95]

    Shinaoka, M

    H. Shinaoka, M. Wallerberger, Y. Murakami, K. Nogaki, R. Sakurai, P. Werner and A. Kauch, Multiscale space-time ansatz for correlation functions of quan- tum systems based on quantics tensor trains , Phys. Rev. X 13, 021015 (2023), doi:10.1103/PhysRevX.13.021015

  87. [96]

    Rohshap, M

    S. Rohshap, M. K. Ritter, H. Shinaoka, J. von Delft, M. Wallerberger and A. Kauch, Two-particle calculations with quantics tensor trains – solving the parquet equations (2024), 2410.22975

  88. [97]

    Vilardi, P

    D. Vilardi, P. M. Bonetti and W. Metzner, Dynamical functional renor- malization group computation of order parameters and critical temperatures in the two-dimensional hubbard model , Phys. Rev. B 102, 245128 (2020), doi:10.1103/PhysRevB.102.245128

  89. [98]

    Hille, The role of the self-energy in the functional renormalization group description of interacting Fermi systems , Ph.D

    C. Hille, The role of the self-energy in the functional renormalization group description of interacting Fermi systems , Ph.D. thesis, Universit¨ at T¨ ubingen (2020). 41

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