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Power-Law Spectra and Asymptotic $ω/T$ Scaling in the Orbital-Selective Mott Phase of a Three-Orbital Hubbard Model

by Fabian Eickhoff

This is not the latest submitted version.

Submission summary

Authors (as registered SciPost users): Fabian Eickhoff
Submission information
Preprint Link: https://arxiv.org/abs/2509.23758v1  (pdf)
Data repository: https://doi.org/10.5281/zenodo.17214657
Date submitted: Sept. 30, 2025, 6:30 p.m.
Submitted by: Fabian Eickhoff
Submitted to: SciPost Physics
Ontological classification
Academic field: Physics
Specialties:
  • Condensed Matter Physics - Theory
  • Condensed Matter Physics - Computational
Approaches: Theoretical, Computational
Disclosure of Generative AI use

The author(s) disclose that the following generative AI tools have been used in the preparation of this submission:

Portions of the text were assisted by AI-based language tools, which were used to improve clarity and grammar. All scientific content, interpretations, and conclusions are the authors’ own.

Abstract

Quantum materials whose properties lie beyond the celebrated Landau Fermi-liquid paradigm have been observed for decades across diverse material platforms. Finding microscopic lattice models for metallic states that exhibit such peculiar behavior remains a major theoretical challenge, as these features often originate from strong quantum fluctuations in strongly interacting electron systems. Here we investigate a three-orbital Hubbard model at a high-symmetry point that hosts a transition from a metallic to an orbital-selective Mott (OSM) phase. Employing single-site dynamical mean-field theory combined with full-density-matrix numerical renormalization group, we chart the $T-U$ phase diagram and obtain high-resolution real-frequency dynamics. In the OSM regime we find asymptotically scale-invariant (power-law) single-particle spectra and asymptotic $\omega/T$ scaling in both charge and spin channels, spanning several decades in frequency and temperature.

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 #3 by Anonymous (Referee 3) on 2025-11-3 (Invited Report)

Strengths

1-Simple model exhibiting \omega/T scaling.
2-Nice scaling analysis.
3-Technical details are provided

Weaknesses

1-The stability of the OSM phase is not entirely clear. How fine-tuned is it?
2-Discussion of scaling of the self-energy is missing.
3-Discussion on the dependence of results on NRG parameters is absent.
4-Motivation and experimental relevance of the model is not completely clear.

Report

In the manuscript, a periodic Anderson model with two conduction bands is studied, with a band structure that results in destructive hybridization interference, as discussed in Ref.[27]. Beyond a critical interaction, an OSM phase is found that features \omega/T scaling. \omega/T scaling is currently discussed and experimentally measured in many strongly correlated materials. This manuscript is an important contribution to this subject.

However, I think it would be valuable and important to discuss how fine-tuned the model is. How important is the special symmetry between the c bands, and can it be spontaneously broken? I understand from Ref.[27] that an asymmetry in the hybridization matrix elements matters, but what about an asymmetry in the dispersion of c_1 and c_2? Is there still a point where the destructive hybridization interference condition is met?

Further, since the OSM phase exhibits an unscreened local moment, is it susceptible to magnetic ordering? If so, will magnetic order change any of the conclusions?

It would also be nice to show and discuss the scaling of the self-energy. I did not see any self-energy data shown in the manuscript, but that data should be readily available.

The author presents a nice scaling analysis and extracts exponents from the data. However, a discussion of the dependence on NRG parameters is absent. How many z-shifts were done? Does the conclusions depend on \Lambda and/or on the broadening parameters? What is the truncation energy, and are the results converged in the number of kept states?

Last, it would be good to explain the motivation of the model in more detail. What are relevant scenarios where the physics discussed here is important? Is the model directly relevant for experimentally realizable systems, or is it more of the conceptually interesting type, i.e. a simple realization of an effect that could possibly occur also in more complicated scenarios? Making the motivation and scope clearer would, in my view, be important. For instance, the author states relevance to non-Fermi liquid transport in several material classes, but my impression is that this and other similar statements are very speculative.

Some minor comments:

1-I find the paragraph on page 3 starting with "We solve the interacting..." confusing. Why are NISQ (the author even introduces an abbreviation that is never used again) devices discussed here? It has nothing to do with the manuscript. Further, the references cited there discuss NISQ devices as DMFT sovlers, so the statement "more elaborate variants systematically approach the full lattice problem" seems incorrect to me. Such a statement would be more appropriate when referring to non-local extensions of DMFT, such as diagrammatic extensions or cluster extensions.

2-In Appendix B, the author describes how he obtains the local Green's function. The approach is very nice, but it is completely unclear to me why multiprecision numerics is needed. A clarification would be nice.

Requested changes

1-Discussion of stability and fine-tuning. What can I expect if the exact symmetry conditions between conduction bands are not met?

2-Discussion of magnetic ordering. Can I expect magnetic ordering, and how would it affect the results?

3-Discussion and presentation of scaling of the self-energy.

4-Discussion of dependence of results on NRG parameters.

5-Clarify the discussion on motivation and experimental relevance.

Recommendation

Ask for minor revision

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

Author:  Fabian Eickhoff  on 2025-12-01  [id 6089]

(in reply to Report 3 on 2025-11-03)

We thank the referee for the careful reading of our manuscript and for the constructive and detailed feedback. We are pleased that the referee finds the model and scaling analysis interesting and recognizes the relevance of $\omega/T$ scaling in the broader context of strongly correlated materials.

Below we address all points raised by the referee and describe the corresponding changes made in the revised manuscript.

  • Stability and fine-tuning of the OSM phase: We have expanded Sec.~4 to clarify under which conditions the destructive hybridization interference is stable. As shown in Ref.[27] and discussed more explicitly now, small deviations in the hybridization matrix elements destroy the OSM phase only below an exponentially small scale. We also added a discussion of asymmetric conduction-band dispersions ($\epsilon_k^1 \neq -\epsilon_k^2$) and explain under which circumstances we expect the interference condition is still met, at least asymptotically near the Fermi surface.

  • Magnetic ordering: As is standard for single-site DMFT, our results apply only above any magnetic ordering temperature $T_{N}$. As discussed in the main text, general considerations suggest that both ferromagnetic and antiferromagnetic ground states may occur, depending on the bandwidth of the correlated orbitals. Importantly, close to the corresponding magnetic phase boundaries the ordering temperature $T_{N}$ is expected to be very small, so that the paramagnetic regime is wide and the scaling results presented here remain valid in this regime

  • Scaling of the self-energy: We thank the referee for this suggestion. We now present the self-energy and its scaling explicitly in a new appendix D, showing its power-law scaling and $\omega/T$ collapse.

  • Dependence on NRG parameters: A detailed scan over NRG hyperparameters has been added to appendix D. We now show the dependence on the number of kept states, the discretization parameter and the broadening parameter. The results confirm that the scaling behavior is robust.

  • Motivation and experimental relevance: We have expanded the discussion in Sec.~2 to clarify the scope and motivation of the model. While we do not claim a direct material realization, we highlight that similar interference effects naturally arise in systems with enlarged unit cells and band folding, including depleted Anderson lattices and moiré structures.

  • Minor comments: (i) The paragraph referring to NISQ devices has been removed. (ii) Appendix B has been revised to clearly explain why multiprecision numerics is needed: the coefficients $p_0$ and $p_1$ scale as $z^2$, making the cubic polynomial ill-conditioned in double precision for small $z = \omega + i\delta$.

Report #2 by Anonymous (Referee 2) on 2025-10-23 (Invited Report)

Strengths

1-High quality state-of-the art numerics (NRG)
2-\omega/T scaling in this model is an interesting result

Weaknesses

1-Model2 is somewhat ad-hoc
2-Connection to a real system or to experiments is not clear or discussed

Report

The paper studies a periodic Anderson model with a particular form of band structure for the conduction electrons that guarantees that Kondo screening cannot fully take place.

The author conducts a state of the art NRG numerical study of this model in the DMFT framework. The main findings are: (i) a detailed phase diagram and (ii) especially, the numerical demonstration of \omega/T scaling in the orbital-selective phase.

This is an interesting result, as this scaling is a hallmark of quantum criticality in several experimental systems. Incidentally, I wouldn't call this scaling 'exotic' - a term used in the conclusion, as this term doesn't mean much and such scaling has been found in several other instances.

The main weakness of the paper is teh absence of an in-depth/convincing discussion of whether abd why this model may have a connection to a material of interest or to \omega/T scaling experimentally observed in a given system.

Overall, the paper is interestinga nd valid and deserves publication in SciPost

Recommendation

Publish (meets expectations and criteria for this Journal)

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

Author:  Fabian Eickhoff  on 2025-12-01  [id 6088]

(in reply to Report 2 on 2025-10-23)

We thank the referee for the positive assessment of our work and for highlighting the quality of the NRG calculations and the interest of the observed $\omega/T$ scaling.

We address the raised points below and have updated the manuscript accordingly.

  • Motivation of the model and experiments: We have clarified the physical motivation for the band-structure symmetry in Sec.~2. As explained there and in Appendix~C, the destructive hybridization interference arises naturally in systems with enlarged real-space unit cells and band folding, such as the depleted periodic Anderson model. While we do not claim a direct material realization, related models are commonly used to describe heavy-fermion materials and, more recently, moiré van der Waals systems as mentioned in Ref[28] of the manuscript.

  • Wording 'exotic scaling': Following the referee's suggestion, we removed the term “exotic scaling” from the conclusion and now simply refer to “scaling.”

Report #1 by Anonymous (Referee 1) on 2025-10-13 (Invited Report)

Strengths

1-Simple, well defined model exhibiting omega/T scaling.
2-Appropriate scaling analysis.
3-Good level of technical detail.

Weaknesses

1-Could include a calculation and discussion of transport properties.
2-The motivation for some parts of text and citations are unclear.

Report

This work analyzes an orbital-selective OSM phase found in a specially tailored three-orbital Hubbard model. Well defined omega/T scaling is found for this exotic phase beyond traditional paradigms. Due to paucity of models showing such behaviour, these results are valuable. The results are obtained with reliable and highly accurate numerical method. The potential impact of the work would be improved if it also presented transport results, optical conductivity and dc resistivity. Since these are easily obtained from the results that the author already has, I strongly suggest those to be included. I have some other minor comments:

  • This work has significant overlap with Ref. [27]. What are the differences in the model and how they are important for the physics?

  • The paragraph starting with "We solve the interacting lattice problem" is difficult to understand. Why is algorithmic complexity relevant for this manuscript? I also don't see any need for citing works on NISQ devices. This seems out of place here. The following paragraph then starts with "We restrict ourselves to..". One should explain what physical features one may lose when working within the DMFT approximation.

  • The discussion around Eq. (6) does not refer to the corresponding figure 3. The same issue for Fig. 4. Admittedly the figures appear on the same pages as the discussion, but nevertheless.

  • "only at intermediate frequencies omega>0".. Can one define some lower-limit and write omega>omega^* instead?

  • Why do the roots need to be obtained with multiprecision numerics (Appendix B.1)?

Requested changes

1-Include discussion of transport properties.

Recommendation

Publish (meets expectations and criteria for this Journal)

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

Author:  Fabian Eickhoff  on 2025-12-01  [id 6087]

(in reply to Report 1 on 2025-10-13)

We thank the referee for the careful reading of our manuscript and for the constructive and helpful feedback.
We are pleased that the referee finds the model well defined, the scaling analysis appropriate, and the technical level solid. We fully agree that transport properties are an important and interesting aspect of this model. Indeed, we are currently working on calculating and analyzing the optical conductivity and dc resistivity. However, in the present study we chose to focus on the scaling and especially the origin of $\omega/T$ scaling of single-particle quantities, and we leave a detailed discussion of transport for future work.

Below we address the referee’s comments, all of which have been incorporated into the revised manuscript:

  • Relation to Ref[27]: In Ref.[27] we studied a closely related model, but the present work extends this analysis in several important directions. Here we consider a \emph{dispersive} $f$-band, include finite-temperature dynamics, and analyze the dynamical spin susceptibility. Moreover, we originally did not expect to find $\omega/T$ scaling in the OSM phase, because the effective impurity problem entering DMFT is not at a quantum critical point. A key result of the present manuscript is that asymptotic $\omega/T$ scaling nevertheless emerges over a wide range of temperatures and frequencies.
  • Algorithmic complexity paragraph: We have removed the discussion related to algorithmic complexity and NISQ computing, as suggested by the referee.
  • Missing figure references: We have added the missing references to the corresponding figures in the discussion around Eq.~(6) and Fig.~4.
  • Frequency condition: We replaced $\omega>0$ with the physically meaningful condition $\omega > T$ in the corresponding paragraph.
  • Multiprecision root finding (Appendix B.1): The coefficients $p_0(z)$ and $p_1(z)$ of the cubic polynomial both scale as $z^{2}$, where $z=\omega+i\delta$ with $\delta = 10^{-15}$. For small $\omega$, this makes the cubic-root problem numerically ill-conditioned in double precision. To reliably resolve the two roots that collapse to zero in this limit, we therefore evaluate Cardano’s formula with high-precision arithmetic. Although alternative approaches may exist, the numerical overhead is negligible, and the use of multiprecision guarantees stability of the DMFT self-consistency loop.

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