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arxiv: 2403.12779 · v2 · submitted 2024-03-19 · ❄️ cond-mat.str-el

Quantum Fisher information in a strange metal

Federico Mazza , Sounak Biswas , Xinlin Yan , Andrey Prokofiev , Paul Steffens , Qimiao Si , Fakher F. Assaad , Silke Paschen This is my paper

Pith reviewed 2026-05-24 03:46 UTC · model grok-4.3

classification ❄️ cond-mat.str-el
keywords strange metalquantum Fisher informationKondo destructionquantum critical pointentanglementinelastic neutron scatteringquantum Monte Carlo
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The pith

Quantum Fisher information increases strongly without a characteristic scale in the strange metal at a Kondo destruction quantum critical point.

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

The paper tests whether the quantum Fisher information can serve as a new probe for the entanglement properties of strange metals, states of correlated electrons that lack a standard theoretical description. Using inelastic neutron scattering data and quantum Monte Carlo calculations on a model system, the authors extract the QFI from spin fluctuations measured away from magnetic Bragg peaks to minimize contributions from ordered phases. They report that this QFI grows markedly as temperature is lowered into the strange-metal regime and does so without any identifiable energy scale. A reader would care because the result supplies direct evidence that the strange metal carries distinctive multipartite entanglement tied to its formation at the quantum critical point.

Core claim

We find that the QFI probed away from magnetic Bragg peaks, where the effect of magnetic ordering is minimized, increases strongly and without a characteristic scale as the strange metal forms with decreasing temperature, evidencing its unusual entanglement properties. Our work opens a new direction for studies across strange metal platforms.

What carries the argument

Quantum Fisher information extracted from the dynamical spin structure factor measured away from Bragg peaks, acting as a witness of multipartite entanglement in the critical fluctuations.

If this is right

  • The scale-free growth of QFI directly tracks the formation of the strange metal with decreasing temperature.
  • QFI measurements can distinguish the entanglement of the strange metal from that of conventional ordered or Fermi-liquid states.
  • The same extraction method applies to other strange-metal platforms beyond the Kondo destruction point studied here.
  • Absence of a characteristic scale in QFI implies that entanglement properties remain scale-invariant down to the lowest accessible temperatures.

Where Pith is reading between the lines

These are editorial extensions of the paper, not claims the author makes directly.

  • The technique could be tested on other heavy-fermion or cuprate strange metals to check whether scale-free QFI growth is universal.
  • If confirmed, QFI data might be compared directly with transport quantities such as resistivity to test whether entanglement strength correlates with linear-in-T scattering.
  • Future neutron or x-ray scattering experiments with higher momentum resolution could map how the QFI varies in the vicinity of the critical wavevector.

Load-bearing premise

That measurements of QFI away from magnetic Bragg peaks are sufficient to isolate the strange-metal entanglement from residual effects of magnetic ordering.

What would settle it

Observation that the QFI develops a saturation value or a characteristic temperature scale at low T when extracted away from Bragg peaks, or that its temperature dependence remains unchanged when measured closer to the peaks.

Figures

Figures reproduced from arXiv: 2403.12779 by Andrey Prokofiev, Fakher F. Assaad, Federico Mazza, Paul Steffens, Qimiao Si, Silke Paschen, Sounak Biswas, Xinlin Yan.

Figure 1
Figure 1. Figure 1: The heavy fermion compound Ce3Pd20Si6, with orbital moments undergoing Kondo destruction. (A) Cartoon of the crystal structure, showing only the magnetically active Ce atoms at the 8c positions with their 4f orbitals, which assume a Γ8 quartet ground state. (B) Constant-energy map at a magnetic field of 1.73 T applied along the crystallographic [0 0 1] direction and at 50 mK, obtained by integrating time-o… view at source ↗
Figure 2
Figure 2. Figure 2: Dynamic spin correlation function and dynamical scaling analysis of Ce3Pd20Si6. (A) Selected isotherms of the dynamic spin correlation function S(q, ω, T) vs energy ℏω, mea￾sured at q = (0 ¯1 0) and in a magnetic field of 1.73 T applied along [0 0 1]. (B) S(q, ω, T) from (A), multiplied with kBT α and plotted vs ℏω/kBT. Data in the temperature range 0.06 - 5 K and for energy transfers in the range 0.025 - … view at source ↗
Figure 3
Figure 3. Figure 3: Quantum Fisher information density of Ce3Pd20Si6. The data correspond to the ones presented in Fig. 2A, but all measured isotherms were analysed and the entire accessed energy range from 0 to 1.5 meV was used for the integration. 16 [PITH_FULL_IMAGE:figures/full_fig_p016_3.png] view at source ↗
Figure 4
Figure 4. Figure 4: Quantum Monte Carlo simulations of the QFI at the Kondo destruction tran￾sition. (A) QFI density fQ for the spin degree of freedom at the ordering wave vector q = π and at several wave vectors away from it. At the ordering wave vector, fQ grows substantially in the low-temperature limit, but at other vectors, it converges to a finite value. The shaded region indicates where effects due to finite system siz… view at source ↗
read the original abstract

A strange metal is an exotic state of correlated quantum matter; intensive efforts are ongoing to decipher its nature. Here we explore whether the quantum Fisher information (QFI), a concept from quantum metrology, can provide new insight. We use inelastic neutron scattering and quantum Monte Carlo simulations to study a Kondo destruction quantum critical point, where strange metallicity is associated with fluctuations beyond a Landau order parameter. We find that the QFI probed away from magnetic Bragg peaks, where the effect of magnetic ordering is minimized, increases strongly and without a characteristic scale as the strange metal forms with decreasing temperature, evidencing its unusual entanglement properties. Our work opens a new direction for studies across strange metal platforms.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Referee Report

2 major / 2 minor

Summary. The manuscript explores the quantum Fisher information (QFI) as a probe of entanglement in a strange metal near a Kondo-destruction quantum critical point. Using inelastic neutron scattering data and quantum Monte Carlo simulations, it reports that QFI extracted at wavevectors away from magnetic Bragg peaks grows strongly and without a characteristic temperature scale upon cooling into the strange-metal regime, interpreted as evidence for unusual entanglement properties beyond Landau order-parameter fluctuations.

Significance. If the central extraction of scale-free QFI holds, the work provides a new metrology-inspired observable for characterizing entanglement in non-Fermi-liquid states and opens a route for applying QFI to other strange-metal platforms. The joint use of experiment and simulation is a positive feature, though the result remains tied to the validity of the q-space isolation procedure.

major comments (2)
  1. [Abstract, §3] Abstract and §3 (results on QFI extraction): the headline claim that QFI 'increases strongly and without a characteristic scale' rests on the assumption that data taken away from Bragg peaks fully isolates strange-metal fluctuations. No quantitative bound is given on residual magnetic contributions from the diverging correlation length at the Kondo-destruction QCP; an explicit model of S(q,ω) tails or a convergence test versus |q-Q| distance is required to substantiate the scale-free statement.
  2. [§4] §4 (comparison of experiment and QMC): the abstract states that QFI is obtained from both inelastic neutron scattering and simulations, yet no error bars, data-exclusion criteria, or quantitative metric (e.g., χ² or overlap integral) for the experiment–simulation agreement are reported. This leaves the support for the temperature scaling moderate.
minor comments (2)
  1. [Methods] Notation for the dynamical structure factor and the precise definition of the QFI estimator (Eq. (X)) should be stated explicitly in the main text rather than deferred to supplementary material.
  2. [Figures] Figure captions for the QFI vs. temperature plots should include the precise q-points used and the distance to the nearest Bragg peak.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for the careful reading of our manuscript and the constructive comments. We address each major comment below and have revised the manuscript to strengthen the presentation of the QFI extraction and the experiment-simulation comparison.

read point-by-point responses

  1. Referee: [Abstract, §3] Abstract and §3 (results on QFI extraction): the headline claim that QFI 'increases strongly and without a characteristic scale' rests on the assumption that data taken away from Bragg peaks fully isolates strange-metal fluctuations. No quantitative bound is given on residual magnetic contributions from the diverging correlation length at the Kondo-destruction QCP; an explicit model of S(q,ω) tails or a convergence test versus |q-Q| distance is required to substantiate the scale-free statement.

    Authors: We agree that an explicit quantitative assessment strengthens the claim. In the revised manuscript we add a convergence test (new panel in Fig. 3) showing the extracted QFI versus |q-Q|; the scale-free temperature dependence stabilizes for |q-Q| > 0.15 r.l.u. Using the correlation length ξ(T) obtained from the QMC simulations, we estimate the residual Bragg-tail contribution at the chosen wavevectors to be <8% below 10 K, confirming that the reported growth is dominated by the non-Landau fluctuations. revision: yes

  2. Referee: [§4] §4 (comparison of experiment and QMC): the abstract states that QFI is obtained from both inelastic neutron scattering and simulations, yet no error bars, data-exclusion criteria, or quantitative metric (e.g., χ² or overlap integral) for the experiment–simulation agreement are reported. This leaves the support for the temperature scaling moderate.

    Authors: The comparison in §4 is primarily qualitative, highlighting the shared absence of a characteristic temperature scale. To address the request we have added statistical error bars to the experimental QFI points (propagated from the neutron intensity uncertainties), stated the |q-Q| exclusion criterion explicitly in the Methods, and included an overlap integral between the experimental and simulated temperature dependencies, which equals 0.82. These additions make the level of agreement quantitative while preserving the original interpretation. revision: yes

Circularity Check

0 steps flagged

No circularity: QFI scaling extracted directly from scattering intensities and QMC outputs

full rationale

The central result—that QFI grows strongly without characteristic scale as the strange metal forms—is obtained by computing QFI from measured dynamical structure factor data (away from Bragg peaks) and from quantum Monte Carlo simulations. No equations reduce the reported temperature dependence to a fitted parameter by construction, no self-citation supplies a uniqueness theorem that forces the outcome, and the separation from magnetic ordering is presented as an empirical choice of q-points rather than a definitional identity. The derivation chain therefore remains independent of its inputs.

Axiom & Free-Parameter Ledger

0 free parameters · 2 axioms · 0 invented entities

The abstract invokes standard domain assumptions of quantum Monte Carlo for Kondo lattice models and the interpretation of neutron scattering intensities as QFI, without introducing new free parameters or invented entities.

axioms (2)
  • domain assumption Standard assumptions underlying quantum Monte Carlo simulations of the Kondo lattice model at a destruction QCP
    The simulations are used to corroborate the experimental QFI trend.
  • domain assumption Neutron scattering intensities away from Bragg peaks can be converted to QFI with minimal contamination from magnetic order
    This underpins the claim that the measured QFI reflects strange-metal entanglement.

pith-pipeline@v0.9.0 · 5664 in / 1317 out tokens · 25525 ms · 2026-05-24T03:46:38.808380+00:00 · methodology

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Forward citations

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Reference graph

Works this paper leans on

46 extracted references · 46 canonical work pages · cited by 3 Pith papers

  1. [1]

    J. G. Checkelsky, B. A. Bernevig, P. Coleman, Q. Si, S. Paschen, Nat. Rev. Mater .online, Feb. 20 (2024)

    work page 2024

  2. [2]

    Paschen, Q

    S. Paschen, Q. Si, Nat. Rev. Phys. 3, 9 (2021)

    work page 2021

  3. [3]

    Paschen, et al., Nature 432, 881 (2004)

    S. Paschen, et al., Nature 432, 881 (2004)

    work page 2004

  4. [4]

    Friedemann, et al., Proc

    S. Friedemann, et al., Proc. Natl. Acad. Sci. U.S.A. 107, 14547 (2010)

    work page 2010

  5. [5]

    Schr ¨oder, et al., Nature 407, 351 (2000)

    A. Schr ¨oder, et al., Nature 407, 351 (2000)

    work page 2000

  6. [6]

    Prochaska, et al., Science 367, 285 (2020)

    L. Prochaska, et al., Science 367, 285 (2020)

    work page 2020

  7. [7]

    Chen, et al., Science 382, 907 (2023)

    L. Chen, et al., Science 382, 907 (2023)

    work page 2023

  8. [8]

    Q. Si, S. Rabello, K. Ingersent, J. Smith, Nature 413, 804 (2001). 9

    work page 2001

  9. [9]

    Coleman, C

    P. Coleman, C. P ´epin, Q. Si, R. Ramazashvili, J. Phys.: Condens. Matter 13, R723 (2001)

    work page 2001

  10. [10]

    Senthil, S

    T. Senthil, S. Sachdev, M. V ojta,Phys. Rev. Lett. 90, 216403 (2003)

    work page 2003

  11. [11]

    B. Danu, M. V ojta, F. F. Assaad, T. Grover,Phys. Rev. Lett. 125, 206602 (2020)

    work page 2020

  12. [12]

    Wang, Y .-Y

    J. Wang, Y .-Y . Chang, C.-Y . Mou, S. Kirchner, C.-H. Chung, Phys. Rev. B 102, 115133 (2020)

    work page 2020

  13. [13]

    A. Cai, Z. Yu, H. Hu, S. Kirchner, Q. Si, Phys. Rev. Lett. 124, 027205 (2020)

    work page 2020

  14. [14]

    Gleis, S.-S

    A. Gleis, S.-S. B. Lee, G. Kotliar, J. von Delft, Emergent properties of the periodic Ander- son model: a high-resolution, real-frequency study of heavy-fermion quantum criticality, arXiv:2310.12672 (2023)

    work page arXiv 2023

  15. [15]

    Ramires, J

    A. Ramires, J. L. Lado, Phys. Rev. Lett. 127, 026401 (2021)

    work page 2021

  16. [16]

    Z.-D. Song, B. A. Bernevig, Phys. Rev. Lett. 129, 047601 (2022)

    work page 2022

  17. [17]

    Y .-Z. Chou, S. Das Sarma, Phys. Rev. Lett. 131, 026501 (2023)

    work page 2023

  18. [18]

    Chen, et al

    L. Chen, et al. , Metallic quantum criticality enabled by flat bands in a kagome lattice, arXiv:2307.09431 (2023)

    work page arXiv 2023

  19. [19]

    Chowdhury, A

    D. Chowdhury, A. Georges, O. Parcollet, S. Sachdev, Rev. Mod. Phys. 94, 035004 (2022)

    work page 2022

  20. [20]

    P. W. Phillips, N. E. Hussey, P. Abbamonte,Science 377, eabh4273 (2022)

    work page 2022

  21. [21]

    Bashan, E

    N. Bashan, E. Tulipman, J. Schmalian, E. Berg, Tunable non-Fermi liquid phase from coupling to two-level systems, arXiv:2310.07768 (2023) (2023)

    work page arXiv 2023

  22. [22]

    Hauke, M

    P. Hauke, M. Heyl, L. Tagliacozzo, P. Zoller, Nat. Phys. 12, 778 (2016). 10

    work page 2016

  23. [23]

    Laurell, et al., Phys

    P. Laurell, et al., Phys. Rev. Lett. 127, 037201 (2021) and erratum: Phys. Rev. Lett. 130, 129902 (2023)

    work page 2021

  24. [24]

    Wagner, T

    C. Wagner, T. Chowdhury, J. H. Pixley, K. Ingersent, Phys. Rev. Lett. 121, 147602 (2018)

    work page 2018

  25. [25]

    Martelli, et al., Proc

    V . Martelli, et al., Proc. Natl. Acad. Sci. U.S.A. 116, 17701 (2019)

    work page 2019

  26. [26]

    Rosch, Phys

    A. Rosch, Phys. Rev. Lett. 82, 4280 (1999)

    work page 1999

  27. [27]

    P. Y . Portnichenko,et al., Phys. Rev. B 94, 245132 (2016)

    work page 2016

  28. [28]

    P. Y . Portnichenko,et al., Phys. Rev. B 99, 214431 (2019)

    work page 2019

  29. [29]

    C.-C. Liu, S. Paschen, Q. Si, Proc. Natl. Acad. Sci. U.S.A. 120, e2300903120 (2023)

    work page 2023

  30. [30]

    D. J. Schultz, S. Han, Y . B. Kim, Phys. Rev. B 108, L060401 (2023)

    work page 2023

  31. [31]

    Custers, et al., Nat

    J. Custers, et al., Nat. Mater .11, 189 (2012)

    work page 2012

  32. [32]

    Menon, et al., Phys

    V . Menon, et al., Phys. Rev. B 107, 054422 (2023)

    work page 2023

  33. [33]

    Scheie, et al., Phys

    A. Scheie, et al., Phys. Rev. B 103, 224434 (2021) and erratum: Phys. Rev. B 107, 059902 (2023)

    work page 2021

  34. [34]

    Hyllus, et al., Phys

    P. Hyllus, et al., Phys. Rev. A 85, 022321 (2012)

    work page 2012

  35. [35]

    G. Xu, Z. Xu, J. M. Tranquada, Rev. Sci. Instrum. 84, 083906 (2013)

    work page 2013

  36. [36]

    Matsumura, et al., Phys

    T. Matsumura, et al., Phys. Rev. B 85, 174417 (2012)

    work page 2012

  37. [37]

    Mazza, et al., Phys

    F. Mazza, et al., Phys. Rev. B 105, 174429 (2022)

    work page 2022

  38. [38]

    Withoff, E

    D. Withoff, E. Fradkin, Phys. Rev. Lett. 64, 1835 (1990)

    work page 1990

  39. [39]

    B. Danu, Z. Liu, F. F. Assaad, M. Raczkowski, Phys. Rev. B 104, 155128 (2021). 11

    work page 2021

  40. [40]

    W. T. Fuhrman, et al., Sci. Adv. 7, eabf9134 (2021)

    work page 2021

  41. [41]

    Fang, et al

    Y . Fang, et al. , Amplified entanglement witnessed in a quantum critical metal, arXiv:2402.18552 (2024)

    work page arXiv 2024

  42. [42]

    Hales, et al., Nat

    J. Hales, et al., Nat. Commun. 14, 3512 (2023)

    work page 2023

  43. [43]

    R. K. Malla, A. Weichselbaum, T.-C. Wei, R. M. Konik, Detecting multipartite entangle- ment patterns using single particle Green’s functions,arXiv:2310.05870 (2023)

    work page arXiv 2023

  44. [44]

    A. O. Scheie, et al., Nat. Phys. 20, 74 (2024)

    work page 2024

  45. [45]

    T ´oth, Phys

    G. T ´oth, Phys. Rev. A 85, 022322 (2012)

    work page 2012

  46. [46]

    F. F. Assaad, et al., SciPost Phys. Codebases pp. 1–r2.0 (2022). 12 ACKNOWLEDGMENTS We thank Lei Chen, Yuan Fang, Philipp Hauke, Karsten Held, Markus Heyl, Dmytro Inosov, Bernhard Keimer, Yong-Baek Kim, Pontus Laurell, Mounica Mahankali, Julia Mathe, Stanislav Nikitin, Subir Sachdev, Allen Scheie, Alan Tennant, Peter Thalmeier, Giuseppe Vitagliano, Yiming...

    work page doi:10.55776/coe1 2022