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Non-perturbative intertwining between spin and charge correlations: A "smoking gun" single-boson-exchange result

by Severino Adler, Friedrich Krien, Patrick Chalupa-Gantner, Giorgio Sangiovanni, Alessandro Toschi

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Submission summary

Authors (as registered SciPost users): Severino Adler · Giorgio Sangiovanni
Submission information
Preprint Link:  (pdf)
Date accepted: 2024-02-01
Date submitted: 2024-01-17 09:25
Submitted by: Adler, Severino
Submitted to: SciPost Physics
Ontological classification
Academic field: Physics
  • Condensed Matter Physics - Theory
  • Condensed Matter Physics - Computational
Approaches: Theoretical, Computational


We study the microscopic mechanism controlling the interplay between local charge and local spin fluctuations in correlated electron systems via a thorough investigation of the generalized on-site charge susceptibility of several fundamental many-electron models, such as the Hubbard atom, the Anderson impurity model, and the Hubbard model. By decomposing the numerically determined generalized susceptibility in terms of physically transparent single-boson exchange processes, we unveil the microscopic mechanisms responsible for the breakdown of the self-consistent many-electron perturbation expansion. In particular, we unambiguously identify the origin of the significant suppression of its diagonal entries in (Matsubara) frequency space and the slight increase of the off-diagonal ones which cause the breakdown. The suppression effect on the diagonal elements originates directly from the electronic scattering on local magnetic moments, reflecting their increasingly longer lifetime as well as their enhanced effective coupling with the electrons. Instead, the slight and diffuse enhancement of the off-diagonal terms can be mostly ascribed to multiboson scattering processes. The strong intertwining between spin and charge sectors is partly weakened at the Kondo temperature due to a progressive reduction of the effective spin-fermion coupling of local magnetic fluctuations in the low frequency regime. Our analysis, thus, clarifies the precise mechanism through which the physical information is transferred between different scattering channels of interacting electron problems and highlights the pivotal role played by such an intertwining in the physics of correlated electrons beyond the perturbative regime.

Author comments upon resubmission

Thank you very much for forwarding the two Referee reports on our
manuscript 2212.09693v4:

*Non-perturbative intertwining between spin and charge correlations: A "smoking gun" single-boson-exchange result*

We are glad that our work has been positively evaluated by the two Referees. In particular, Referee 1 finds that we *``have addressed the points raised by the previous referees in a satisfactory manner"*, and evaluates the significance of our study as *``high"*. Similarly, Referee 2 thinks that *``the quality of the research is excellent"*, also rating the significance of our study as *``high"* and the validity of our results as *``top"*.

Both Referees appear in favor of publication of our manuscript, after we consider their specific observations aimed at further improving the readability and the impact of our manuscript.

Herewith we resubmit our manuscript carefully revised, after having addresses all the questions raised by the two Referees, as we illustrate in our detailed replies.
Hence, we hope that our revised manuscript can be now accepted for publication in Sci. Post. Phys.

Thank you very much for your assistance,
Sincerely yours,
S. Adler, F. Krien, P. Chalupa-Gantner, G. Sangiovanni, and A. Toschi

List of changes

1.) Adapted the text improve readability. See attached .pdf to the replies to the Referees.

2.) Used full names of the models in Sec. 2.2.

3.) Added a couple of sentences at the end of the first paragraph of Sec. 2.3 to mention why one might need to invert the generalized susceptibilities and to draw the readers attention to the related problems of diagrammatic approaches, stemming from divergences of the two-particle irreducible charge vertex.

4.) Added a sentence in Sec. 2.3 mentioning the possible physical implications of the sign-change of the eigenvalues, which could not occur in absence of the selective suppression of the diagonal entries of the generalized charge susceptibility.

5.) Added a sentences to highlight the formal connection of the diagonal and offdiagonal elements of $\chi^{\text{ch}}_{\nu\nu'}$ to the ``bubble`` and two-particle vertex correction term in Sec. 2.3 right after Eq. (8).

6.) Included the explicit expression of inversion of BSE as reason for divergences on page 12.

7.) Moved Sec. 3.4 into the appendix, and inserted a concise summary of its content at the end of Sec. 3.3.

8.) Corrected a Typo in Fig. 11.

Published as SciPost Phys. 16, 054 (2024)

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