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REVIEW 3 major objections 6 minor 66 references

Possibility of BCS-BEC crossover in $\kappa$-type organic superconductors

T0 review · 3 major / 6 minor · reviewed 2026-08-12 · deepseek-v4-flash

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Pith's one-line read At 6 percent doping, an organic superconductor hits BCS-BEC crossover

desk verdict Careful VMC study shows a plausible BCS-BEC crossover at δ=0.06 in a model for κ-HgBr, but the material-level claim depends on an untested Hg2+ suppression of the stripe phase at δ=0.11. read the letter →

arxiv 2411.15510 v2 pith:QN7YGWUN submitted 2024-11-23 cond-mat.supr-con cond-mat.str-el

Hiroshi Watanabe , Hiroaki Ikeda This is my paper · ORCID
classification cond-mat.supr-concond-mat.str-el
keywords BCS-BECcrossoverorganicsuperconductorκ-(BEDT-TTF)4Hg2.89Br8extendedHubbardmodelvariationalMonteCarlosuperfluidweightcoherencelengthstripeorder
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 claims that BCS-BEC crossover, normally seen in ultracold atoms, can occur in a repulsively interacting four-band model of κ-type organic superconductors, but only at a specific hole doping δ=0.06. At δ=0 the system becomes a Mott insulator before pairing gets strong, and at δ=0.11 a stripe-charge-ordered phase appears; both mask the crossover. At δ=0.06, the superconducting correlation function grows then falls while the local pairing gap keeps rising, the coherence length kFξ saturates near one, and the superfluid weight and chemical-potential indicators change in the expected crossover pattern. The paper argues that κ-HgBr, whose nonstoichiometric mercury content and triangular-lattice frustration suppress competing orders, sits near this doping and is a concrete candidate. It also proposes that other κ-type materials could be tuned into the same regime by pressure, chemical substitution, or gated doping.

What carries the argument

The central machinery is the four-band extended Hubbard model on the κ-type lattice, whose unit cell has four BEDT-TTF molecules and whose hopping parameters are taken from first-principles estimates for κ-CN. The paper uses a Gutzwiller-Jastrow type variational wavefunction with charge and spin Jastrow factors plus an optimized one-body part containing renormalized transfer integrals, a renormalized chemical potential, and a real-space superconducting gap. It evaluates four BCS-BEC crossover markers: superconducting correlation function PSC, coherence length via kFξ = kF·ℏvF/(π∆̃), normalized superfluid weight Ds/D0s from the curvature of the energy in a vector potential, and renormalized chemical potential µ̃/EF. The pairing symmetry is extended-s+dx2-y2 with the largest real-space gap on the h bond. The combination of geometric frustration from the near-isotropic triangular dimer lattice and the specific doping δ=0.06 is what suppresses Mott and stripe order long enough for the crossover indicators to appear.

What would settle it

Measure the low-temperature charge and spin order of κ-HgBr under pressure at its stoichiometric filling: observing a stripe phase with charge period four and spin period eight near δ≈0.11, or finding that the effective doping is not near δ=0.06, would contradict the paper's claim. A direct calculation of the true chemical potential showing µ/EF dropping below zero before U/t=10.5 would also undermine the proposed crossover criterion.

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Extended reading notes

Core claim

The paper concludes, from variational Monte Carlo calculations of the four-band extended Hubbard model, that the BCS-BEC crossover occurs at hole doping δ=0.06 but not at δ=0 or δ=0.11. In the model, the crossover manifests as a dome-shaped superconducting correlation function PSC with a monotonically increasing local gap ∆̃, coherence length kFξ shrinking to order one, normalized superfluid weight Ds/D0s falling faster than mass renormalization alone would predict, and the ratio µ̃/EF changing from increasing to decreasing. The authors emphasize that this crossover is reached only where competing phases are suppressed: at δ=0 the Mott transition cuts off superconductivity, and at δ=0.11 a C4S8 stripe charge order does the same. They also find a distinctive feature of repulsive lattice systems: the chemical potential stays on the order of EF, rather than dropping below zero as in Fermi gases, which they attribute to strong correlation localizing a fraction of carriers. Because κ-HgBr lacks both Mott insulating and magnetic order, they identify it as a probable material realization of this crossover.

Load-bearing premise

The whole identification of κ-HgBr as a crossover material rests on the assumption that the real material behaves like the δ=0.06 model, even though its stoichiometric doping is δ=0.11; the model excludes the proposed Hg2+-ion effect that would suppress the stripe order.

Editorial extensions

If this is right

  • If the conclusion holds, tuning a κ-type organic superconductor to δ≈0.06 should reveal the full crossover signature: a dome-shaped Tc, kFξ of order one, and a superfluid weight that drops faster than effective mass alone.
  • For κ-HgBr specifically, the model supports attributing the measured low superfluid density and pressure-dependent coherence length to placement in the crossover region at ambient pressure.
  • The same calculation implies that at half-filled δ=0 the crossover is unobservable because the Mott transition intervenes, and at δ=0.11 a four-period charge, eight-period spin stripe order intervenes.
  • The proposed strategy for other κ-type materials is to combine physical and chemical pressure, controlled hole doping by electric-double-layer transistors, and frustration tuning by uniaxial pressure to reach the crossover window.
  • In repulsively interacting lattice systems the crossover is not signaled by µ̃/EF crossing zero; the plateau of µ on the order of EF with decreasing mobile quasiparticle weight is the expected marker.

Reading between the lines

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

  • A direct experimental test is to determine the effective hole doping of κ-HgBr under pressure and whether any stripe charge order appears; the paper's conclusion depends on Hg2+ ions suppressing the δ=0.11 stripe phase, a mechanism the model does not include.
  • The model's prediction of a C4S8 stripe phase at δ=0.11 suggests looking for stripe-like spin and charge modulations in κ-type salts whose doping is near one-eighth, paralleling cuprate physics.
  • If the true chemical potential rather than the variational µ̃ were computed, the authors' interpretation could be sharpened; the current µ̃/EF criterion is qualitative and could shift the estimated crossover boundary.
  • One could search for a bosonic molecular-pair precursor above Tc at δ≈0.06, for example in Nernst or diamagnetic response, as a distinctive consequence of the BEC side.
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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 / 6 minor

Summary. The paper uses variational Monte Carlo (VMC) on a four-band extended Hubbard model for the κ-type organic superconductor κ-HgBr, with transfer integrals taken from band-structure calculations for κ-CN and V/U ratios fixed by a 1/r ansatz. For hole doping δ=0.06, the authors find that superconducting correlations survive into the strongly correlated regime, with a dome in the superconducting correlation function PSC, a monotonically increasing variational gap Δ̃, kFξ approaching O(1), a smoothly decreasing superfluid weight Ds, and a non-monotonic chemical-potential ratio μ̃/EF. They interpret these as indicators of BCS-BEC crossover. At δ=0 the model instead shows a Mott transition, and at δ=0.11 a C4S8 stripe charge-ordered phase. The conclusion assigns the crossover to the real material κ-HgBr by arguing that Hg2+ ions in the insulating layers suppress the stripe order, an effect not included in the model.

Significance. If the central claim holds, the paper would provide a concrete mechanism and a candidate material for BCS-BEC crossover in a repulsively interacting lattice system, beyond ultracold atoms. The strengths are the systematic VMC treatment with several complementary observables, the use of model parameters from prior band-structure work rather than fitting the crossover, and the explicit acknowledgment of limitations in the chemical potential and superfluid-weight calculations. The model calculation at δ=0.06 is credible and internally consistent. The load-bearing weakness is the bridge from the model to κ-HgBr: the material assignment depends on an untested assumption that Hg2+ ions suppress the stripe phase at the stoichiometric doping δ=0.11, where the model itself predicts no crossover.

major comments (3)
  1. [Conclusion, first paragraph] The material-level claim for κ-HgBr rests on the assertion that, although stoichiometry gives δ=0.11, the charge-ordered phase is suppressed by Hg2+ ions in the insulating layers, an effect explicitly not included in the model. The model at δ=0.11 instead stabilizes a C4S8 stripe phase for U/t>8.9 (Fig. 2(d)) and shows no BCS-BEC crossover. Unless this suppression is demonstrated—for example by extending the model to include the anion-layer degrees of freedom, or by citing experimental evidence that rules out stripe order in κ-HgBr—the claim that κ-HgBr realizes the crossover is not established. The calculation supports a model scenario at δ=0.06, but the title and abstract imply a stronger material realization. This needs to be either supported or explicitly reframed as a prediction conditional on the effective doping being near δ=0.06.
  2. [Section III.A, Fig. 2(c)] The quantitative crossover criterion kFξ = kF · ħvF/(π Δ̃) uses the optimized variational amplitude Δ̃ rather than the true superconducting gap, and the authors acknowledge in Section III.C that μ̃ and EF may deviate from the true values. Since the crossover region is assigned to U/t>10.5 using this criterion, the precise location is variational. A convergence or sensitivity check—for example comparing the kFξ behavior with the long-range SC correlation function and with the superfluid-weight downturn—would strengthen the claim that the crossover is not an artifact of the trial wave function.
  3. [Section III.C, Fig. 4] The chemical-potential criterion is non-standard: μ̃/EF remains of order EF and the crossover is inferred from a change from increasing to decreasing behavior, whereas the usual BCS-BEC crossover signature is μ≲0. The reinterpretation in terms of strongly correlated electron localization and a reduced number of mobile quasiparticles is plausible but not derived from the variational wave function. If μ̃/EF is to be used as one of the four supporting indicators, the relation between μ̃ and the true chemical potential, and the meaning of the turning point, should be made more explicit.
minor comments (6)
  1. [Title page and affiliations] There are typos in the affiliations: 'Ritsumei kan' should be 'Ritsumeikan' and 'S higa' should be 'Shiga'.
  2. [Abstract and Conclusion] The abstract states that κ-HgBr is the case where Mott insulating and magnetic orders are absent, but the model at δ=0.11 finds a stripe charge order. The text should clarify that the material assignment relies on an effective doping near δ=0.06 rather than the stoichiometric value.
  3. [Section III.A, Fig. 2(a)] The blue-shaded area is labeled 'BCS-BEC crossover region' in the caption, but the criterion for where this region begins is not defined in the caption or in the main text until later; defining it explicitly would improve clarity.
  4. [Section III.A, after Fig. 2] The statement that the decrease in PSC is a 'true' order parameter (~Tc) is imprecise: PSC is a ground-state correlation function, not a transition temperature. The intended analogy should be phrased more carefully.
  5. [Section III.A, U/t>12.5 discussion] The claim that an inhomogeneous state emerges for U/t>12.5 is based on the variational energy depending on the initial Monte Carlo configuration, but no quantitative evidence (e.g., energy differences or order-parameter profiles) is shown. This is presented as expectation rather than a demonstrated phase, and it should be labeled as such.
  6. [References] Reference [61] is cited as an arXiv preprint (arXiv:2205.03682); if it has been published in the interim, the published version should be cited.

Circularity Check

0 steps flagged · score 0.0 of 10

No circularity: the BCS-BEC crossover at δ=0.06 is a new VMC output computed from an externally fixed Hamiltonian; the only caveat is an untested material-level assumption, not a circular step.

full rationale

The derivation chain is self-contained. The four-band extended Hubbard model (Eq. 1) uses transfer integrals from a DFT parameter set for κ-CN (Ref. 36) and Coulomb ratios fixed by a 1/r ansatz; none of the reported target observables—PSC, kFξ, Ds/D0s, μ̃/EF—is used as an input or fitting constraint. The crossover claim is read off from the U/t dependence of these independently computed quantities, and the phase diagram as a function of doping (Mott at δ=0, stripe at δ=0.11, crossover at δ=0.06) is a new result of the VMC calculation rather than an input. Self-citations (Refs. 34, 35 for the Hamiltonian and gap symmetry; Refs. 50, 62 for cuprate comparisons) supply the starting model and analogies, but the present calculation of the PSC dome and competing orders is independent support, so they do not raise the circularity score. The main limitation, stated in the Conclusion, is the bridge to κ-HgBr: the paper assumes that Hg2+ ions suppress the stripe phase at nominal δ=0.11 to bring the material to an effective doping near δ=0.06, an effect explicitly not included in the model. That is an untested physical assumption and a robustness/correctness risk, but it is not circular because it does not redefine the calculated crossover in terms of the material claim. Similarly, the use of the variational μ̃ rather than the true chemical potential is acknowledged as an approximation, not a circular step. No equation reduces by construction to its inputs.

Assumptions & free parameters 1 free parameters · 5 assumptions · 0 invented entities

The paper introduces no new physical entities; the phase factor P_dim_theta is a variational tool, not a new particle or force. The main assumptions are standard VMC methodology, the transfer of band parameters from κ-CN to κ-HgBr, the 1/r form of intersite interactions, the use of variational µ̃ as a physical proxy, and the unmodeled Hg2+ suppression of stripe order.

free parameters (1)
  • V/U ratios for intersite Coulomb interactions = (Vb1,Vb2,Vp,Vq)/U = (0.5, 0.28, 0.33, 0.29)
    The intersite Coulomb interactions are fixed relative to U by assuming a 1/r dependence (Refs. 36, 46, 47). This is a model choice that affects the phase boundaries and hence the doping window where the crossover appears.
assumptions (5)
  • domain assumption The variational Monte Carlo wavefunction with Gutzwiller and Jastrow factors accurately captures the ground state of the four-band extended Hubbard model.
    The method is standard but uncontrolled; the accuracy depends on the flexibility of the trial state. The paper uses it without benchmarks against exact results for this model.
  • domain assumption The transfer integrals estimated for κ-CN apply to κ-HgBr.
    Used in Section II because a band calculation for κ-HgBr is not available. The validity is argued by similar triangular lattice and susceptibility, but not proven.
  • domain assumption The intersite Coulomb interaction ratios follow a 1/r dependence.
    Set in Section III.A to (Vb1,Vb2,Vp,Vq)/U = (0.5, 0.28, 0.33, 0.29) based on Refs. 36, 46, 47. This choice influences the stripe phase location.
  • domain assumption The variational chemical potential µ̃ and the noninteracting EF provide a valid criterion for the BCS-BEC crossover.
    The authors state in Section III.C that µ̃ may deviate from the true µ and that obtaining the true values is left for future work.
  • ad hoc to paper Hg2+ ions in the insulating layers suppress the stripe charge order not included in the model.
    Stated in the Conclusion to reconcile the model's δ=0.11 stripe phase with the nominal doping of κ-HgBr. No microscopic calculation is provided.

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Pith. "Pith review of Possibility of BCS-BEC crossover in $\kappa$-type organic superconductors." pith.science (2026). https://pith.science/paper/QN7YGWUN

@misc{pith2026241115510,
  author       = {Pith},
  title        = {Pith review of: Possibility of BCS-BEC crossover in $\kappa$-type organic superconductors},
  year         = {2026},
  howpublished = {\url{https://pith.science/paper/QN7YGWUN}},
  note         = {Machine review of arXiv:2411.15510}
}
abstract

The realization of BCS-BEC crossover in superconductors, which smoothly connects Bardeen-Cooper-Schrieffer (BCS) theory with Bose-Einstein Condensation (BEC) in fermion systems, is an intriguing recent topic in strongly correlated electron systems. The organic superconductor $\kappa$-(BEDT-TTF)$_4$Hg$_{2.89}$Br$_8$ ($\kappa$-HgBr) under pressure is one of the leading candidates, owing to its unique metallic spin-liquid nature and tunable electron correlation. We theoretically investigate the extended Hubbard model for $\kappa$-HgBr and discuss the possibility of the BCS-BEC crossover by systematically calculating superconducting correlation function, coherence length, superfluid weight, and chemical potential. Our findings show that the BCS-BEC crossover can be observed when competing phases, such as Mott insulators and charge and/or spin orders, are suppressed by appropriate hole doping. $\kappa$-HgBr is just the case because both the Mott insulating phase and magnetic orders are absent due to its nonstoichiometric Hg composition and geometrical frustration. We further propose that other $\kappa$-type organic superconductors could serve as potential candidates of the BCS-BEC crossover if their band fillings and degree of geometrical frustration are systematically tuned.

Figures

Figures reproduced from arXiv: 2411.15510 by the authors.

Figure 1
Figure 1. FIG. 1. (a) Schematic lattice structure of the [PITH_FULL_IMAGE:figures/full_fig_p002_1.png] view at source ↗
Figure 2
Figure 2. (a) shows the U/t dependence of PSC for different hole doping rates δ. The ratio be￾tween U and intersite Coulomb interactions is fixed as (Vb1 ,Vb2 ,Vp,Vq)/U=(0.5, 0.28, 0.33, 0.29), assuming a 1/r-dependence [36, 46, 47]. For δ = 0 (576 holes/576 dimers), PSC increases with increasing U/t, displaying BCS-like behavior, and then drops discontinuously to ap￾proximately zero at U/t ≈ 7.7 due to the Mott transi￾tion (… view at source ↗
Figure 3
Figure 3. FIG. 3 [PITH_FULL_IMAGE:figures/full_fig_p004_3.png] view at source ↗
Figures from the paper (4 more)
Figure 4
Figure 4. Figure 4: FIG. 4 [PITH_FULL_IMAGE:figures/full_fig_p005_4.png]
Figure 5
Figure 5. Figure 5: FIG. 5. (a) Band structure and (b) Fermi surface for [PITH_FULL_IMAGE:figures/full_fig_p006_5.png]
Figure 6
Figure 6. Figure 6: FIG. 6. Schematic picture of hopping processes with addi [PITH_FULL_IMAGE:figures/full_fig_p007_6.png]
Figure 7
Figure 7. Figure 7: FIG. 7 [PITH_FULL_IMAGE:figures/full_fig_p008_7.png]

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Works this paper leans on

66 extracted references · 60 canonical work pages

  1. [1]

    D. M. Eagles, Possible Pairing without Superconductiv- ity at Low Carrier Concentrations in Bulk and Thin-Film Superconducting Semiconductors, Phys. Rev. 186, 456 (1969)

    work page 1969

  2. [2]

    Indeed, Pα (r) shows good convergence for r /greaterorsimilar4, and we take an av- erage up to r ≈ 10 to define it as Pα

    (3) If Pα (r) converges to a finite value as |r| = r → ∞ , su- perconducting long-range order is present. Indeed, Pα (r) shows good convergence for r /greaterorsimilar4, and we take an av- erage up to r ≈ 10 to define it as Pα . We calculate Pα up to the 15th-neighbor bond ( b1, b2, p, q, h, . . . ), with the largest value taken as the superconducting corre...

    work page

  3. [3]

    Quantum Liquid Crys- FIG. 5. (a) Band structure and (b) Fermi surface for κ-HgBr. High symmetry points are Γ(0,0), Y( π/R x), Z( π/ 2Ry), and M(π/R x, π/ 2Ry). tals

    06 but not at δ = 0 or δ = 0 . 11 in the present model. Appropriate hole doping suppresses competing orders, al- lowing the BCS-BEC crossover to emerge. Most κ-type organic superconductors correspond to δ = 0, where the Mott transition takes place before reaching the BCS-BEC crossover region. In contrast, κ-HgBr, with δ away from zero, has the potential t...

    work page

  4. [4]

    A. J. Leggett, Diatomic molecules and cooper pairs, Lect . Notes Phys. 115, 13 (1980)

    work page 1980

  5. [5]

    Nozi` eres and S

    P. Nozi` eres and S. Schmitt-Rink, Bose condensation in an attractive fermion gas: From weak to strong coupling superconductivity, J. Low Temp. Phys. 59, 195 (1985)

    1985

  6. [6]

    Randeria, J.-M

    M. Randeria, J.-M. Duan, L.-Y. Shieh, Bound States, Cooper Pairing, and Bose Condensation in Two Dimen- sions, Phys. Rev. Lett. 62, 981 (1989)

    work page 1989

  7. [7]

    Q. Chen, J. Stajic, S. Tan, and K. Levin, BCS–BEC crossover: From high temperature superconductors to ul- tracold superfluids, Phys. Rep. 412, 1 (2005)

    work page 2005

  8. [8]

    G. C. Strinati, P. Pieri, G. R¨ opke, P. Schuck, and M. Urban, The BCS–BEC crossover: From ultra-cold Fermi gases to nuclear systems, Phys. Rep. 738, 1 (2018). 9

    work page 2018

Show all 66 references
  1. [9]

    Greiner, C

    M. Greiner, C. A. Regal, and D. S. Jin, Emergence of a molecular Bose-Einstein condensate from a Fermi gas, Nature 426, 537 (2003)

    2003

  2. [10]

    C. A. Regal, M. Greiner, and D. S. Jin, Observation of Resonance Condensation of Fermionic Atom Pairs, Phys. Rev. Lett. 92, 040403 (2004)

    2004

  3. [11]

    Randeria and E

    M. Randeria and E. Taylor, Crossover from Bardeen- Cooper-Schrieffer to Bose-Einstein Condensation and the Unitary Fermi Gas, Annu. Rev. Condens. Matter Phys. 5, 209 (2014)

    2014

  4. [12]

    Yanase, T

    Y. Yanase, T. Jujo, T. Nomura, H. Ikeda, T. Hotta, and K. Yamada, Theory of superconductivity in strongly cor- related electron systems, Phys. Rept. 387, 1 (2003)

    2003

  5. [13]

    J. Sous, Y. He, and S. A. Kivelson, Absence of a BCS-BEC crossover in the cuprate superconductors, npj Quantum Mater. 8, 25 (2023)

    2023

  6. [14]

    Kasahara, T

    S. Kasahara, T. Watashige, T. Hanaguri, Y. Kohsaka, T. Yamashita, Y. Shimoyama, Y. Mizukami, R. Endo, H. Ikeda, K. Aoyama, T. Terashima, S. Uji, T. Wolf, H. von L¨ ohneysen, T. Shibauchi, Y. Matsuda, Field-induced superconducting phase of FeSe in the BCS-BEC cross- over, Proc....

    2014

  7. [15]

    Rinott, K

    S. Rinott, K. B. Chashka, A. Ribak, E. D. L. Rienks, A. Taleb-Ibrahimi, P. Le Fevre, F. Bertran, M. Randeria, and A. Kanigel, Tuning across the BCS-BEC crossover in the multiband superconductor Fe1+ySexTe1−x: An angle-resolved photoemission study, Sci. Adv. 3, e1602372 (2017)

    2017

  8. [16]

    B¨ oker, P

    J. B¨ oker, P. A. Volkov, K. B. Efetov, and I. Eremin, s+is superconductivity with incipient bands: Doping de- pendence and STM signatures, Phys. Rev. B 96, 014517 (2017)

    2017

  9. [17]

    Hashimoto, Y

    T. Hashimoto, Y. Ota, A. Tsuzuki, T. Nagashima, A. Fukushima, S. Kasahara, Y. Matsuda, K. Matsuura, Y. Mizukami, T. Shibauchi, S. Shin, and K. Okazaki, Bose-Einstein Condensation Superconductivity Induced by Disappearance of the Nematic State, Sci. Adv. 6, eabb9052 (2020)

    2020

  10. [18]

    Suzuki, K

    Y. Suzuki, K. Wakamatsu, J. Ibuka, H. Oike, T. Fujii, K. Miyagawa, H. Taniguchi, and K. Kanoda, Mott-Driven BEC-BCS Crossover in a Doped Spin Liquid Candidate κ-(BEDT-TTF)4Hg2.89Br8, Phys. Rev. X 12, 011016 (2022)

    2022

  11. [19]

    Imajo, T

    S. Imajo, T. Kobayashi, Y. Matsumura, T. Maeda, Y. Nakazawa, H. Taniguchi, and K. Kindo, Pseudogap for- mation in organic superconductors, Phys. Rev. Materials 7, 124803 (2023)

    2023

  12. [20]

    Nakagawa, Y

    Y. Nakagawa, Y. Kasahara, T. Nomoto, R. Arita, T. No- jima, and Y. Iwasa, Gate-controlled BCS-BEC crossover in a two-dimensional superconductor, Science 372, 190 (2021)

    2021

  13. [21]

    Q. J. Chen, Z. Q. Wang, R. Boyack, S. L. Yang, and K. Levin, When superconductivity crosses over: From BCS to BEC, Rev. Mod. Phys. 96, 025002 (2024)

    2024

  14. [22]

    Reyes, M

    D. Reyes, M. A. Continentino, F. Deus, and C. Thomas, Tail-like regime and BCS-BEC crossover due to hy- bridization in a two-band superconductor, J. Phys.: Con- dens. Matter 30, 175601 (2018)

    2018

  15. [23]

    Yerin, H

    Y. Yerin, H. Tajima, P. Pieri, and A. Perali, Coexis- tence of giant Cooper pairs with a bosonic condensate and anomalous behavior of energy gaps in the BCS-BEC crossover of a two-band superfluid Fermi gas, Phys. Rev. B 100, 104528 (2019)

    2019

  16. [24]

    Tajima, Y

    H. Tajima, Y. Yerin, P. Pieri, and A. Perali, Mechanisms of screening or enhancing the pseudogap throughout the two-band Bardeen-Cooper-Schrieffer to Bose-Einstein condensate crossover, Phys. Rev. B 102, 220504(R) (2020)

    2020

  17. [25]

    N. Witt, Y. Nomura, S. Brener, R. Arita, A. I. Lichten- stein, and T. O. Wehling, Bypassing the lattice BCS- BEC crossover in strongly correlated superconductors through multiorbital physics, npj Quantum Mater. 9, 100 (2024)

    2024

  18. [26]

    R. N. Lyubovskaya, E. A. Zhilyaeva, A. V. Zvarykina, V. N. Laukhin, R. B. Lyubovskii, and S. I. Pesotskii, Is the organic metal (ET) 4Hg3Br8 a quasi-2D superconductor?, JETP Lett. 45, 530 (1987)

    1987

  19. [27]

    R. N. Lyubovskaya, E. I. Zhilyaeva, S. I. Pesotskii, R. B. Lyubovskii, L. O. Atovmyan, O. A. D’yachenko, and T. G. Takhirov, Superconductivity of (ET) 4Hg2.89Br8 at atmospheric pressure and Tc = 4. 3K and the critical-field anisotropy, JETP Lett. 46, 188 (1987)

    1987

  20. [28]

    H. Oike, K. Miyagawa, H. Taniguchi, and K. Kanoda, Pressure-Induced Mott Transition in an Organic Super- conductor with a Finite Doping Level, Phys. Rev. Lett. 114, 067002 (2015)

    2015

  21. [29]

    H. Oike, Y. Suzuki, H. Taniguchi, Y. Seki, K. Miyagawa, and K. Kanoda, Anomalous Metallic Behaviour in the Doped Spin Liquid Candidate κ-(ET)4Hg2.89Br8, Nat. Commun. 8, 756 (2017)

    2017

  22. [30]

    Kino and H

    H. Kino and H. Fukuyama, Phase Diagram of Two- Dimensional Organic Conductors: (BEDT-TTF) 2X, J. Phys. Soc. Jpn. 65, 2156 (1996)

    1996

  23. [31]

    Seo, Charge Ordering in Organic ET Compounds, J

    H. Seo, Charge Ordering in Organic ET Compounds, J. Phys. Soc. Jpn. 69, 805 (2000)

    2000

  24. [32]

    Kuroki, T

    K. Kuroki, T. Kimura, R. Arita, Y. Tanaka, and Y. Matsuda, dx2−y2 - versus dxy- like pairings in organic superconductors κ-(BEDT-TTF)2X, Phys. Rev. B 65, 100516(R) (2002)

    2002

  25. [33]

    Hotta, Quantum electric dipoles in spin-liquid dime r Mott insulator κ-ET2Cu2(CN)3, Phys

    C. Hotta, Quantum electric dipoles in spin-liquid dime r Mott insulator κ-ET2Cu2(CN)3, Phys. Rev. B 82, 241104(R) (2010)

    2010

  26. [34]

    Naka and S

    M. Naka and S. Ishihara, Electronic Ferroelectricity i n a Dimer Mott Insulator, J. Phys. Soc. Jpn. 79, 063707 (2010)

    2010

  27. [35]

    M. Naka, S. Hayami, H. Kusunose, Y. Yanagi, Y. Mo- tome, and H. Seo, Spin current generation in organic an- tiferromagnets, Nat. Commun. 10, 4305 (2019)

    2019

  28. [36]

    Watanabe, H

    H. Watanabe, H. Seo, and S. Yunoki, Phase Com- petition and Superconductivity in κ-(BEDT-TTF)2X: Importance of Intermolecular Coulomb interactions, J. Phys. Soc. Jpn. 86, 033703 (2017)

    2017

  29. [37]

    Watanabe, H

    H. Watanabe, H. Seo, and S. Yunoki, Mechanism of su- perconductivity and electron-hole doping asymmetry in κ-type molecular conductors, Nat. Commun. 10, 3167 (2019)

    2019

  30. [38]

    Koretsune and C

    T. Koretsune and C. Hotta, Evaluating model parame- ters of the κ- and β ′-type Mott insulating organic solids, Phys. Rev. B 89, 045102 (2014)

    2014

  31. [39]

    Shimizu, K

    Y. Shimizu, K. Miyagawa, K. Kanoda, M. Maesato, and G. Saito, Spin Liquid State in an Organic Mott Insulator with a Triangular Lattice, Phys. Rev. Lett. 91, 107001 (2003)

    2003

  32. [40]

    W. L. McMillan, Ground State of Liquid He 4, Phys. Rev. 138, A442 (1965)

    1965

  33. [41]

    Ceperley, G

    D. Ceperley, G. V. Chester, and M. H. Kalos, Monte Carlo simulation of a many-fermion study, Phys. Rev. B 16, 3081 (1977). 10

    1977

  34. [42]

    Yokoyama and H

    H. Yokoyama and H. Shiba, Variational Monte-Carlo Studies of Hubbard Model. I, J. Phys. Soc. Jpn. 56, 1490 (1987)

    1987

  35. [43]

    Sorella, Generalized Lanczos algorithm for variati onal quantum Monte Carlo, Phys

    S. Sorella, Generalized Lanczos algorithm for variati onal quantum Monte Carlo, Phys. Rev. B 64, 024512 (2001)

    2001

  36. [44]

    Yunoki and S

    S. Yunoki and S. Sorella, Two spin liquid phases in the spatially anisotropic triangular Heisenberg model, Phys. Rev. B 74, 014408 (2006)

    2006

  37. [45]

    B. J. Powell and R. H. McKenzie, Symmetry of the su- perconducting order parameter in frustrated systems de- termined by the spatial anisotropy of spin correlations, Phys. Rev. Lett. 98, 027005 (2007)

    2007

  38. [46]

    Guterding, M

    D. Guterding, M. Altmeyer, H. O. Jeschke, and R. Va- lent ´ ı, Near-degeneracy of extendeds + dx2−y2 and dxy order parameters in quasi-two-dimensional organic super- conductors Phys. Rev. B 94, 024515 (2016)

    2016

  39. [47]

    Zantout, M

    K. Zantout, M. Altmeyer, S. Backes, and R. Valent ´ ı, Superconductivity in correlated BEDT-TTF molecular conductors: Critical temperatures and gap symmetries, Phys. Rev. B 97, 014530 (2018)

    2018

  40. [48]

    Nakamura, Y

    K. Nakamura, Y. Yoshimoto, T. Kosugi, R. Arita, and M. Imada, Ab initio Derivation of Low-Energy Model for κ-ET Type Organic Conductors, J. Phys. Soc. Jpn. 78, 083710 (2009)

    2009

  41. [49]

    Yoshimi, T

    K. Yoshimi, T. Misawa, T. Tsumuraya, and H. Seo, Com- prehensive Ab Initio Investigation of the Phase Diagram of Quasi-One-Dimensional Molecular Solids, Phys. Rev. Lett. 131, 036401 (2023)

    2023

  42. [50]

    Kanoda, Metal–Insulator Transition in κ-(ET)2X and (DCNQI)2M: Two Contrasting Manifestation of Electron Correlation, J

    K. Kanoda, Metal–Insulator Transition in κ-(ET)2X and (DCNQI)2M: Two Contrasting Manifestation of Electron Correlation, J. Phys. Soc. Jpn. 75, 051007 (2006)

    2006

  43. [51]

    J. M. Tranquada, B. J. Sternlleb, J. D. Axe, Y. Naka- mura, and S. Uchida, Evidence for stripe correlations of spins and holes in copper oxide superconductors, Nature 375, 561 (1995)

    1995

  44. [52]

    Watanabe, T

    H. Watanabe, T. Shirakawa, K. Seki, H. Sakakibara, T. Kotani, H. Ikeda, and S. Yunoki, Monte Carlo study of cuprate superconductors in a four-band d-p model: role of orbital degrees of freedom, J. Phys.: Condens. Matter 35, 195601 (2023)

    2023

  45. [53]

    R. H. McKenzie, Similarities Between Organic and Cuprate Superconductors, Science 278, 820 (1997)

    1997

  46. [54]

    Paramekanti, M

    A. Paramekanti, M. Randeria, and N. Trivedi, High- Tc superconductors: A variational theory of the supercon- ducting state, Phys. Rev. B 70, 054504 (2004)

    2004

  47. [55]

    V. J. Emery and S. A. Kivelson, Frustrated electronic phase separation and high-temperature superconductors, Physica C 209, 597 (1993)

    1993

  48. [56]

    A. J. Millis and S. N. Coppersmith, Variational wave functions and the Mott transition, Phys. Rev. B 43, 13770 (1991)

    1991

  49. [57]

    D. J. Scalapino, S. R. White, and S. C. Zhang, Insulator, metal, or superconductor: The criteria, Phys. Rev. B 47, 7995 (1993)

    1993

  50. [58]

    Het´ enyi, Drude Weight, Meissner Weight, Rotationa l Inertia of Bosonic Super fluids: How Are They Distin- guished?, J

    B. Het´ enyi, Drude Weight, Meissner Weight, Rotationa l Inertia of Bosonic Super fluids: How Are They Distin- guished?, J. Phys. Soc. Jpn. 83, 034711 (2014)

    2014

  51. [59]

    Tamura and H

    S. Tamura and H. Yokoyama, Drude and Superconduct- ing Weights and Mott Transition in Variation Theory, J. Phys. Soc. Jpn. 84, 064707 (2015)

    2015

  52. [60]

    Merino, B

    J. Merino, B. J. Powell, and R. H. McKenzie, Ferromag- netism, paramagnetism, and a Curie-Weiss metal in an electron-doped Hubbard model on a triangular lattice, Phys. Rev. B 73, 235107 (2006)

    2006

  53. [61]

    Watanabe, H

    T. Watanabe, H. Yokoyama, Y. Tanaka, and J. Inoue, Superconductivity and a Mott Transition in a Hubbard Model on an Anisotropic Triangular Lattice, J. Phys. Soc. Jpn. 75, 074707 (2006)

    2006

  54. [62]

    Y. J. Uemura, L. P. Le, G. M. Luke, B. J. Stern- lieb, W. D. Wu, J. H. Brewer, T. M. Riseman, C. L. Seaman, M. B. Maple, M. Ishikawa, D. G. Hinks, J. D. Jorgensen, G. Saito, and H. Yamochi, Basic Simi- larities among Cuprate, Bismuthate, Organic, Chevrel- Phase, and Heavy-Ferm...

    1991

  55. [63]

    Wakamatsu, Y

    K. Wakamatsu, Y. Ueno, K. Miyagawa, H. Taniguchi, and K. Kanoda, Reduced superfluid density in a doped spin liquid candidate, arXiv: 2205.03682

    arXiv

  56. [64]

    Watanabe, T

    H. Watanabe, T. Shirakawa, K. Seki, H. Sakakibara, T. Kotani, H. Ikeda, and S. Yunoki, Unified description of cuprate superconductors using a four-band d-p model, Phys. Rev. Research 3, 033157 (2021)

    2021

  57. [65]

    Kawasugi, K

    Y. Kawasugi, K. Seki, Y. Edagawa, Y. Sato, J. Pu, T. Takenobu, S. Yunoki, H. M. Yamamoto, and R. Kato, Electron–hole doping asymmetry of Fermi surface recon- structed in a simple Mott insulator, Nat. Commun. 7, 12356 (2016)

    2016

  58. [66]

    H. Oike, K. Miyagawa, H. Taniguchi, H. Okamoto, and K. Kanoda, Metal-insulator transition via control of spin liquidity in a doped Mott insulator, arXiv: 2202.06032

    arXiv

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