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Superconductivity enhancement and particle-hole asymmetry: interplay with electron attraction in doped Hubbard model

by Zhi Xu, Hong-Chen Jiang, Yi-Fan Jiang

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Submission summary

Authors (as registered SciPost users): Yi-Fan Jiang
Submission information
Preprint Link: scipost_202508_00079v1  (pdf)
Code repository: https://github.com/JiangYF-phys/U1code
Date submitted: Aug. 31, 2025, 4:40 p.m.
Submitted by: Yi-Fan Jiang
Submitted to: SciPost Physics
Ontological classification
Academic field: Physics
Specialties:
  • Condensed Matter Physics - Computational
Approach: Computational

Abstract

The role of near-neighbor electron attraction $V$ in strongly correlated systems has been at the forefront of recent research of unconventional superconductivity. However, its implications in the doped Hubbard model on expansive systems remain predominantly unexplored. In this study, we employ the density-matrix renormalization group to examine its effect in the lightly doped $t$-$t'$-Hubbard model on six-leg square cylinders, where $t$ and $t'$ are the first and second neighbor electron hopping amplitudes. In the electron-doped regime ($t'>0$), we find that attractive $V$ can substantially enhance superconducting correlations, driving the system into a pronounced superconducting phase when the attraction exceeds a modest value $V_c \approx 0.5t$. In contrast, in the hole-doped regime ($t' <0$), while heightened superconducting correlations have also been observed in the charge stripe phase, the systems remain insulating with pronounced charge density wave order. Our results demonstrate the importance of the electron attraction in boosting superconductivity in broader doped Hubbard systems and highlight the asymmetry between the electron and hole-doped regimes.

Author indications on fulfilling journal expectations

  • Provide a novel and synergetic link between different research areas.
  • Open a new pathway in an existing or a new research direction, with clear potential for multi-pronged follow-up work
  • Detail a groundbreaking theoretical/experimental/computational discovery
  • Present a breakthrough on a previously-identified and long-standing research stumbling block
Current status:
Has been resubmitted

Reports on this Submission

Report #2 by Anonymous (Referee 2) on 2025-10-5 (Invited Report)

  • Cite as: Anonymous, Report on arXiv:scipost_202508_00079v1, delivered 2025-10-05, doi: 10.21468/SciPost.Report.12067

Strengths

1- interesting finding that electron and hole-doped sides of the high-Tc Hubbard SC react very differently to the addition of a NN attractive interaction

Weaknesses

1- more data points would be needed on the hole-doped side (now only V=0 and V=0.6 t are shown) to make a truly convincing case.

Report

This paper by Xu et al. performs a highly interesting study, how the addition of a NN attraction to the t-t'-Hubbard model affects its superconducting properties. The study is extremely timely, the paper is well written and the results are notable: The authors find that the NN attraction V turns the system into a clean d-wave SC on the electron-doped side, whereas the SC correlations remain decaying exponentially on the hole doped side for the reported values of V. These results certainly fulfill the acceptance criteria of Sci Post Physics, if the following points can be addressed by the authors:

Requested changes

1- The authors should show more data for the hole-doped side, t'<0. Currently, only one set of results at V=0.6 t is shown, which (although impressive) in my view is not sufficient to make a really strong case. On the electron-doped side the authors scan V=0, 0.2 t, 0.4 t, ... 1.0 t in Fig. 2, and one keeps wondering why they didn't perform a similar analysis on the hole-doped side. I understand that in the Wigner crystal phase they cannot extract Luttinger exponents, but it would be interesting to show e.g. how the magnitude of the SC amplitude itself (at a certain distance, say) changes with V. It would also be interesting to see whether some response can be found before V exceeds 1.0 t, or if even larger values of V would be needed (eventually I assume the system should also become superconducting on the hole-doped side?).

2- it would be good to show some convergence data of the overall density profile. The oscillations in Fig. 2 appear well converged, but it is unclear what quantity exactly the authors plotted: is <n(x)> summed over all legs y? Can the authors directly show <n(x,y)> in the supplements, to give a better idea how well the data is converged?

Recommendation

Publish (surpasses expectations and criteria for this Journal; among top 10%)

  • validity: top
  • significance: top
  • originality: top
  • clarity: top
  • formatting: excellent
  • grammar: excellent

Report #1 by Anonymous (Referee 1) on 2025-9-30 (Invited Report)

  • Cite as: Anonymous, Report on arXiv:scipost_202508_00079v1, delivered 2025-09-30, doi: 10.21468/SciPost.Report.12029

Weaknesses

The power-law form of SC and CDW correlations, as well as the continuous change of the exponent as a function of interaction strength, is closely related to the case of the Luther-Emery liquid in one dimension. The numerical observation is very likely an artifact of DMRG calculations on long cylinders. It would be better if the authors could clarify this issue either by comparing the results for cylinders of different widths (e.g., 4-leg and 6-leg) or by providing theoretical references regarding the instability of coupled chains described by the Luther-Emery liquid fixed point.

Report

Using density matrix renormalization approach, the authors studied the doped t-t'-Hubbard model in the presence of a finite attractive nearest neighbour interaction. This calculation is very relevant for understanding the effect of electron phone effect for High-temperature superconductivity. The authors thoroughly investigated the competition between the d-wave superconductivity and the charge density wave order, and the enhancement of superconducting correlation is observed as the V interaction increases. On the other hand, the authors found no evidence of superconducting order in the case of hole doping. This work is timely, well written and definitely deserves publication.

Recommendation

Publish (meets expectations and criteria for this Journal)

  • validity: ok
  • significance: good
  • originality: ok
  • clarity: high
  • formatting: good
  • grammar: good

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