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Evidence of pseudogap and absence of spin magnetism in the time-reversal-symmetry-breaking state of Ba$_{1-x}$K$_x$Fe$_2$As$_2$

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Pith's one-line read High-field NMR shows the time-reversal-symmetry-breaking state in Ba1−xKxFe2As2 at magic doping is preceded by a pseudogap and is free of spin magnetism.

desk verdict The pseudogap NMR data are a genuinely new and useful result; the absence-of-spin-magnetism claim is oversold because the 8 T measurements may not be in the BTRS phase at all. read the letter →

arxiv 2501.11936 v1 pith:6UNHE37W submitted 2025-01-21 cond-mat.supr-con cond-mat.str-el

Florian Bärtl , Nadia Stegani , Federico Caglieris , Ilya Shipulin , Yongwei Li , Quanxin Hu , Yu Zheng , Chi-Ming Yim
show 8 more authors
Sven Luther Jochen Wosnitza Rajib Sarkar Hans-Henning Klauss Julien Garaud Egor Babaev Hannes Kühne Vadim Grinenko
This is my paper · ORCID
classification cond-mat.supr-concond-mat.str-el
keywords time-reversalsymmetrybreakingelectronquadruplingpseudogapnuclearmagneticresonancemuonspinrotationiron-basedsuperconductorspin-latticerelaxationKnightshift
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

This paper argues that the time-reversal-symmetry-breaking (BTRS) state observed above the superconducting transition in Ba1−xKxFe2As2 near x≈0.77 is an electronic condensate, not a magnetic phase. From 75As nuclear magnetic resonance and muon-spin-rotation Knight-shift data, it establishes two connected results: a pseudogap opens at a temperature T* well above the BTRS transition, indicating preformed bound electron pairs, and the spin-lattice relaxation rate shows no enhancement or line broadening through the transition, ruling out spin magnetism and proximity to a magnetic instability. The claim matters because it narrows the origin of the observed spontaneous fields to persistent real-space currents and connects the pseudogap to the predicted precursor of a four-electron (quadrupling) condensate.

What carries the argument

The load-bearing observable is the 75As nuclear spin-lattice relaxation rate 1/T1T, which is proportional to the q-averaged low-energy dynamic spin susceptibility; a magnetic instability would show up as an enhancement near the transition, and none is observed. This is paired with the NMR linewidth (a measure of the distribution of local fields) and the NMR and muon Knight shifts (measures of the static spin susceptibility). The interpretive machinery is the electron-quadrupling scenario, in which the order parameter is fourth order in fermionic fields, ⟨ΔaΔb*⟩≠0 while the individual pairing fields ⟨Δa⟩=0, so BTRS occurs through interband relative-phase locking without spin order, and the pseudogap at T* marks the precursor formation of non-condensed Cooper pairs.

What would settle it

Measure 75As NMR 1/T1T and linewidth on the same doping at fields of about 1–3 T, where the spontaneous Nernst signal clearly marks $T_c^{{Z2}}$; a peak or step in 1/T1T or line broadening at $T_c^{{Z2}}$ would contradict the claim that the transition is non-magnetic, whereas continued monotonic behavior would confirm it.

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Extended reading notes

Core claim

The paper's central claim is that the broken-time-reversal-symmetry state in Ba1−xKxFe2As2 near x≈0.77 is a non-magnetic electronic condensate with a distinct spectral signature: a pseudogap that develops at T* well above $T_c^{{Z2}}$, the temperature where the Z2 symmetry is spontaneously broken. The 75As spin-lattice relaxation rate 1/T1T begins to decrease below T* and keeps decreasing through $T_c^{{Z2}}$ and Tc, with no sign of critical slowing of spin fluctuations, and the NMR linewidth shows no broadening across either transition. Together with NMR and muon-spin-rotation Knight shifts that show no Curie-Weiss behavior, the authors conclude that the spontaneous magnetic fields detected by zero-field muon-spin rotation do not come from spin order or proximity to a magnetic instability, but from persistent real-space currents associated with interband phase locking of the multicomponent order parameter. The pseudogap is interpreted as the fingerprint of non-condensed Cooper pairs that form prior to the fermion-quadrupling ordering, consistent with theory and with specific-heat, transport, and muon-shift data.

Load-bearing premise

The argument assumes that the ordered time-reversal-breaking state still exists, at least in a small residual form, at the 8 T field where the NMR and muon-spin-rotation data were recorded, even though the spontaneous Nernst signal that defines $T_c^{{Z2}}$ could not be resolved at that field.

Editorial extensions

If this is right

  • The time-reversal-symmetry-breaking state above Tc in this compound is a fermion-quadrupling condensate rather than a magnetic phase.
  • The absence of low-energy spin-fluctuation enhancement rules out proximity to a spin-density-wave or other magnetic instability at the magic doping level.
  • The pseudogap T* is a genuine electronic spectral feature observable by NMR, setting the energy scale for pair formation before quadrupling ordering.
  • The spontaneous Nernst signal and the spontaneous magnetic fields detected in zero-field muon-spin rotation share a common origin in persistent currents from interband phase locking.
  • Other iron-based superconductors with reported pseudogaps and BTRS superconductivity may host quartic states at appropriate doping levels, and NMR pseudogap signatures offer a way to search for them.

Reading between the lines

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

  • A testable extension would be to measure 1/T1T across a range of potassium dopings: if the pseudogap is the universal precursor of quadrupling, its separation from Tc should systematically widen as the magic doping is approached from either side.
  • A direct check of the paper's field-extrapolation assumption would be NMR at fields of about 1–3 T, where the spontaneous Nernst signal clearly marks T_c^{Z2}; a feature in 1/T1T or the linewidth there would challenge the non-magnetic interpretation, whereas continued monotonic behavior would strengthen it.
  • The same probe combination could distinguish spin-current from orbital-current loop-order candidates in other time-reversal-symmetry-breaking superconductors by looking for the absence of low-energy spin fluctuations at the ordering transition.
  • Because the Knight shift is suppressed below T*, the underlying gapped density of states appears spin-singlet-like; fitting the temperature dependence with a Yosida-type form could quantify the gap and test whether it matches the specific-heat anomaly scale.
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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

2 major / 4 minor

Summary. This paper reports 75As NMR and transverse-field µSR measurements on Ba1−xKxFe2As2 with x ≈ 0.77, with the aim of probing the electronic spectral properties of the time-reversal-symmetry-breaking (BTRS) state that sets in above Tc. The authors identify a decrease of the spin-lattice relaxation rate 1/T1T below a pseudogap temperature T* that lies above the extrapolated BTRS temperature T_c^Z2 and above Tc, and they associate this with the formation of preformed electron pairs that precede the proposed electron quadrupling condensate. They also find no NMR line broadening and no enhancement of 1/T1T near the extrapolated T_c^Z2 at 8 T, which they interpret as excluding spin magnetism and as evidence that the spontaneous fields seen by zero-field µSR arise from persistent real-space currents rather than from spin order. The paper includes detailed sample characterization, transport, Nernst, and specific-heat data, and a Ginzburg-Landau analysis of field-induced suppression of the BTRS phase.

Significance. If the conclusions hold, this would be the first direct spectroscopic evidence for a pseudogap tied to the proposed fermion quadrupling state above Tc in this material, and it would strengthen the case for nonmagnetic, current-based origin of the spontaneous fields. The paper combines several complementary probes (NMR, µSR, transport, specific heat, STM) and is unusually candid about limitations, explicitly stating in Section II that the quadrupling state cannot be confirmed at the 8 T measurement field and in Appendix F that the mean-field GL analysis is not valid close to Tc. The comparison with literature NMR data (Hirano et al.) and the detailed sample characterization are assets. However, the central absence-of-spin-magnetism conclusion depends on an extrapolation of the BTRS phase boundary to 8 T, and the primary pseudogap evidence in Fig. 4 is presented without visible error bars, so the strength of the claims currently exceeds what the data justify.

major comments (2)
  1. [Section II and IV] The claim that the NMR data "prove the absence of a magnetic transition at T_c^Z2" (abstract and Section IV) is not supported by the data shown, because all NMR and µSR measurements were taken at 8 T. Section II states that the spontaneous Nernst signal "cannot be resolved at 8 T and beyond" and that the authors "cannot determine whether the quadrupling state is completely suppressed, or if a small quadrupling phase remains." The dashed extrapolation of T_c^Z2 in Fig. 1(d) is not a measurement, and the GL analysis in Appendix F explicitly shows that external fields can restore TRS, with the text concluding that for the parameters examined "weaker fields eliminate the quartic phase" (Section F.3). Consequently, the absence of an NMR anomaly near the extrapolated T_c^Z2 at 8 T does not constrain the zero-field BTRS state. This affects the second central conclusion of the paper and must be addressed, either by adding lower-field NMR data where the Nernst signal is resolvable or by substantially tempering the claims in the abstract and Section IV.
  2. [Fig. 4 and Section IV] The primary evidence for the pseudogap is the decrease of 1/T1T below T*(NMR) shown in Fig. 4, but no error bars are visible in this figure. The text states that 1/T1T is "constant within error bars" above T* and that the decrease below T* is monotonous, yet without visible uncertainties the reader cannot assess the significance of the trend, the precise location of the kink, or the claimed absence of an enhancement near T_c^Z2. Please add error bars (or state explicitly how the scatter defines the uncertainty and why the trend is statistically significant) so that the central pseudogap claim can be independently evaluated.
minor comments (4)
  1. [Section IV] The doping level is given as x = 0.776(1) in the first paragraph of Section IV and in Fig. 4, but as x = 0.766(1) in Section II, the Methods, and Fig. 2. Please correct the typo.
  2. [Fig. 2 and Section III] In Fig. 2(b)-(d) the vertical dotted lines are labeled Tc and T*, but the text discusses crossing T_c^Z2; please also mark T_c^Z2 (or explain why it is not marked, given that the measurements are at 8 T).
  3. [Appendix B.2] The sentence "we compare this to the quadrupole frequencies measured by Hirano et al. ." has a missing citation number and an extra period; please fix the reference formatting.
  4. [Section II] The phrase "The theoretical analysis ... demonstrates the mechanism of suppression of the quadrupling state when the external magnetic field exceeds a certain value" is stronger than what the finite-element simulations support, since they are performed for specific parameter sets; suggest "is consistent with" or "illustrates".

Circularity Check

0 steps flagged · score 0.0 of 10

No significant circularity: the central NMR/µSR results are new measurements interpreted within an existing framework; nothing reduces to its inputs by construction.

full rationale

The paper's central empirical content—75As NMR spectra, 1/T1T, linewidth, Knight shift, and 8 T µSR Knight-shift data—is presented as new measurements, not as consequences of the quadrupling theory. The pseudogap assignment is made by identifying a slope change in measured 1/T1T and comparing it with transport and specific-heat anomalies; the electron-quadrupling framework is then used as an interpretive hypothesis, not as the source of the data points. The absence-of-spin-magnetism conclusion rests on the observed monotonic 1/T1T and absence of line broadening, which are direct experimental facts; while the 8 T field may suppress or weaken the zero-field BTRS phase—the paper explicitly says 'we cannot determine whether the quadrupling state is completely suppressed, or if a small quadrupling phase remains at that field'—that is a validity or extrapolation concern, not a circularity. The theoretical finite-element GL analysis is parameterized from a microscopic model and used to test consistency with the observed field suppression; it does not define the measured quantities. Self-citations are present (Refs. [4,5,9,19,20,21]) for prior evidence of T_c^Z2 and the quadrupling scenario, but those prior results are independent experimental or Monte-Carlo results rather than the present paper's own fitted inputs, and the present paper's claims do not reduce to them by construction. No equation is declared to be predicted by another equation that contains it, and no fitted parameter is renamed as a prediction. Accordingly, no specific circular step can be exhibited.

Assumptions & free parameters 4 free parameters · 5 assumptions · 2 invented entities

The central experimental claim rests on a small set of measured crossover temperatures and on the interpretation of NMR and muSR data. Most of the theoretical structure is inherited from prior work by the same group, and the Ginzburg-Landau simulation parameters are illustrative rather than fitted. The main free parameters are the T* assignments and the peak-decomposition parameters; the main assumptions are standard NMR formulas, the bulk relevance of the nanocluster decomposition, the pseudogap interpretation of the 1/T1T drop, and the correctness of the prior identification of the quartic state.

free parameters (4)
  • T*(NMR) = ~12 K at 8 T, ~10.5 K at 16 T
    Crossover temperature defined by the onset of the 1/T1T decrease; the central pseudogap claim depends on this assignment.
  • High-temperature gap Delta_PG = 76 K for x=0.766(1)
    Obtained from an exponential fit 1/T1T proportional to exp(-Delta_PG/T)+const to data above 25 K; used to characterize the high-temperature gapped behavior but not essential to the pseudogap claim.
  • Two-Gaussian NMR decomposition parameters = linewidths and positions of peaks A and B
    The NMR spectra are fit with two overlapping Gaussian peaks; the linewidth and Knight-shift conclusions depend on this decomposition and on the attribution to K-rich and K-poor nanoclusters.
  • Ginzburg-Landau simulation coefficients = u_GammaM=0.5, u_GammaGamma'=0.4875, K^(1)=1.0, K^(2)=0.1 or 0.95, K^(3)=0.015, e=0.5, B0=0.6
    Chosen model parameters for the finite-element demonstration that an external field suppresses T_c^Z2; they are not fitted to the NMR data and are acknowledged as not uniquely determined by experiment.
assumptions (5)
  • standard math 1/T1T is proportional to the q-summed dynamic spin susceptibility (Eq. 2)
    Standard NMR relaxation formula used to infer the absence of low-energy spin fluctuations near T_c^Z2.
  • domain assumption The Knight shift is proportional to the static spin susceptibility with a temperature-independent orbital offset
    Used to interpret the NMR and µSR Knight shifts as spin susceptibility; the orbital contribution is assumed constant over the measured range.
  • domain assumption The two NMR spectral peaks arise from K-rich and K-poor nanoclusters and do not affect global electronic properties
    Supported by STM surface images but extrapolated to the bulk; if one peak reflects a different local environment, the extracted T* could be distorted.
  • domain assumption The drop in 1/T1T below T* reflects a loss of low-energy electronic density of states, not a change in the magnetic-fluctuation background
    Central to the pseudogap claim; no independent calculation of the magnetic-fluctuation contribution is provided.
  • domain assumption The BTRS transition at T_c^Z2 and the electron quadrupling interpretation from previous work [4,5] are correct
    The paper's framing depends on the prior identification of T_c^Z2 via the spontaneous Nernst effect and specific heat.
invented entities (2)
  • Electron quadrupling (quartic) order parameter with non-zero <Delta_a Delta_b*> and zero <Delta_a> independent evidence
    purpose: Explains time-reversal symmetry breaking above Tc without a conventional pairing amplitude or spin order
    This entity is not introduced by the present paper but is assumed from prior theory; it has falsifiable handles such as fractional vortices and a specific-heat anomaly, and this paper adds consistency arguments but no direct observation of the order parameter.
  • Persistent real-space loop currents near defects independent evidence
    purpose: Produce the spontaneous magnetic fields detected by zero-field muSR without spin magnetism
    Loop currents are inferred from the absence of spin magnetism and the presence of spontaneous fields; they are not directly imaged in this work.

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Pith. "Pith review of Evidence of pseudogap and absence of spin magnetism in the time-reversal-symmetry-breaking state of Ba$_{1-x}$K$_x$Fe$_2$As$_2$." pith.science (2026). https://pith.science/paper/6UNHE37W

@misc{pith2026250111936,
  author       = {Pith},
  title        = {Pith review of: Evidence of pseudogap and absence of spin magnetism in the time-reversal-symmetry-breaking state of Ba$_1-x$K$_x$Fe$_2$As$_2$},
  year         = {2026},
  howpublished = {\url{https://pith.science/paper/6UNHE37W}},
  note         = {Machine review of arXiv:2501.11936}
}
abstract

Muon-spin-rotation ($\mu$SR) experiments and the observation of a spontaneous Nernst effect indicate time-reversal symmetry breaking (BTRS) at $T_{\rm c}^{\rm Z2}$ above the superconducting transition temperature $T_{\rm c}$ in Ba$_{1-x}$K$_x$Fe$_2$As$_2$, with $x\approx0.8$. Further studies have pointed out that BTRS is caused by the formation of a new state of matter associated with the condensation of pairs of electron pairs. Despite exhibiting multiple unconventional effects that warrant further investigation, the electronic spectral properties of this electron quadrupling state remain largely unexplored. Here, we present detailed $^{75}$As nuclear magnetic resonance (NMR) measurements of Ba$_{1-x}$K$_x$Fe$_2$As$_2$, with $x = 0.77$, which has $T_{\rm c}^{\rm Z2}$ > $T_{\rm c}$ according to measurements of the spontaneous Nernst effect. The NMR data obtained in this work provide the first direct electronic spectral characteristics of the electron quadrupling state by indicating that it evolves from a pseudogap that sets in at $T^*$ well above $T_{\rm c}^{\rm Z2}$. This pseudogap behavior is consistent with $\mu$SR Knight-shift, specific-heat, and transport data indicating the formation of a bound state of electrons. According to a theory of electron quadrupling condensates, such bound-state formations should precede the onset of BTRS correlations between pairs of electron pairs. The second important insight from NMR data is the absence of spin-related magnetism. The temperature dependence of the spin-lattice relaxation rate $1/T_1T$ and the evolution of the NMR linewidth prove the absence of a magnetic transition at $T_{\rm c}^{\rm Z2}$ and rule out even a proximity to some magnetic instability. This indicates that the spontaneous magnetic fields detected in this compound are not caused by spin magnetism but are associated with persistent real-space currents.

Figures

Figures reproduced from arXiv: 2501.11936 by the authors.

Figure 1
Figure 1. Physical properties of the Ba1−xKxFe2As2 crystal with x = 0.766(1). Temperature dependence of (a) the electrical resistivity, ρxx, (b) the spontaneous Nernst effect, Sxy, and (c) the change of the specific heat across the superconduct￾ing transition, ∆C/T, measured at different magnetic fields applied along the c direction. (d) Magnetic field phase diagram of the critical temperatures obtained using various techniqu… view at source ↗
Figure 2
Figure 2. (d) shows the temperature-normalized intensity of all recorded 75As NMR spectra, which is obtained by integration over frequency of the entire spectrum at a given temperature. At high temperatures, the intensity is constant within error bars. Exactly at Tc , the RF shielding causes a sharp drop in intensity. Upon closer inspection, the intensity is already slightly reduced in the temperature regime T ∗ > Tc . We can… view at source ↗
Figure 3
Figure 3. (a) Fourier transform of the TF µSR time spec￾tra measured at about 8 T and selected temperatures for Ba1−xKxFe2As2 with x = 0.75(2). The arrows indicate dif￾ferent components of the signal: I and II are muons stopping at two different sites of the sample, and Ag denotes a signal from muons stopping in the silver sample holder. (b) Tem￾perature dependence of the µSR Knight shift measured at about 8 T, applied along … view at source ↗
Figures from the paper (14 more)
Figure 4
Figure 4. Figure 4: Temperature dependence of the 75As nuclear spin￾lattice relaxation rate 1/T1T (black rectangles), the specific￾heat difference divided by T (green circles), and the magne￾toresistance in the inset (blue triangles) at 8 T. The dot￾ted, vertical lines mark the critical t…
Figure 5
Figure 5. Figure 5: 2Θ X-ray scans measured from both sides of the [PITH_FULL_IMAGE:figures/full_fig_p009_5.png]
Figure 6
Figure 6. Figure 6: Temperature-dependent magnetic susceptibility of [PITH_FULL_IMAGE:figures/full_fig_p010_6.png]
Figure 7
Figure 7. Figure 7: shows the angular-dependent NMR spectra over a range of ±15° [ [PITH_FULL_IMAGE:figures/full_fig_p010_7.png]
Figure 8
Figure 8. Figure 8: Potassium-doping dependence of the quadrupole [PITH_FULL_IMAGE:figures/full_fig_p011_8.png]
Figure 9
Figure 9. Figure 9: Temperature dependence of the resonance frequency [PITH_FULL_IMAGE:figures/full_fig_p011_9.png]
Figure 10
Figure 10. Figure 10: Spin-lattice relaxation rate 1/T1T for x = 0.766(1) (red circles), compared to data for x = 1, 0.69, 0.55, and 0.39 (gray rectangles, blue triangles, green triangles, and purple diamonds, respectively) from Hirano et al. [35]. The colored arrows mark Tc for the corres…
Figure 11
Figure 11. Figure 11: Temperature-dependent 1/T1T data for Ba1−xKxFe2As2 samples with x = 0.766(1) (squares) and x = 0.69 (triangles). The latter data are taken from Hirano et al. [35]. The black arrows denote Tc. The data at high temperatures are compared to an exponential fit (green dash…
Figure 12
Figure 12. Figure 12: Temperature dependence of the spin-lattice re [PITH_FULL_IMAGE:figures/full_fig_p013_12.png]
Figure 14
Figure 14. Figure 14: (a) Atomically-resolved topographic image taken [PITH_FULL_IMAGE:figures/full_fig_p014_14.png]
Figure 15
Figure 15. Figure 15: (a) Temperature dependence of the electrical re [PITH_FULL_IMAGE:figures/full_fig_p014_15.png]
Figure 16
Figure 16. Figure 16: Schematic view of the gap structure in the first [PITH_FULL_IMAGE:figures/full_fig_p015_16.png]
Figure 17
Figure 17. Figure 17: Simulations of field-heated experiments. Note that increasing the temperature puts the system closer to [PITH_FULL_IMAGE:figures/full_fig_p018_17.png]
Figure 18
Figure 18. Figure 18: Average values of order parameters ⟨|ψa|⟩ and ⟨ny⟩ as a function of temperature compared for the ground state with simulations in an external field (B0 = 0.6). Here, ny = 2Im(ψ ∗ 1ψ2)/Ψ †Ψ is the order parameter that measures the spontaneous breakdown of the time-reve…

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Reference graph

Works this paper leans on

65 extracted references · 60 canonical work pages · cited by 1 Pith paper

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    The obtained c- axis parameter corresponds to x = 0.766(1) [40], indicating that the doping level is the same within 0.1% for both sides of the sample

    X-ray measurements 2 04 06 08 01 001 201 40101 1 02 1 03 1 04 1 05 B a0 .234K0 .766Fe2 As2 I ntensity (counts)2 Θ (deg) side A side Bc-axis13.65467 /s849113.65574 /s8491 Figure 5: 2Θ X-ray scans measured from both sides of the sample used for the NMR measurements. The obtained c- axis parameter corresponds to x = 0.766(1) [40], indicating that the doping ...

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    Susceptibility 0 2 4 6 8 1 01 21 4- 10 4π χ, B| |c = 0.5 mT, NMR sample χ' /χ' (2K), BA C| |c = 10 μT μS R sample 4π χ, B| |c = 0.5 mT, STM sample M agnetic susceptibilityT emperature (K)F CZ FCB a1 -xKx Fe2 As2 Figure 6: Temperature-dependent magnetic susceptibility of the single crystals used for the NMR and STM measurements as well as of the stack of t...

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    Sample orientation For the NMR measurements, we utilized the angu- lar dependence of the 75As Knight shift to orient the Ba1−xKxFe2As2 sample in magnetic field. At 10 K and 8 T, the angular-dependent shift yields a squared-sine-type behavior, where the maximum of the shift corresponds to a field orientation parallel to the crystallographic c axis. Fig. 7 ...

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    Confirmation of bulk potassium stoichiometry In order to confirm the potassium doping level of our sample by means of NMR, we determined the quadrupole frequency νQ by measuring the central transition and the higher-frequency satellite transition at 20 K and 8 T (in- set of Fig. 8). Since, in the present case, the c axis is the principle axis of the elect...

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    For this, we monitored changes of the complex radio-frequency (RF) reflection coefficient S11 at the NMR circuit, using a vector net- work analyzer

    Superconducting transitions probed by RF penetration As a confirmation of the superconducting phase dia- gram of our NMR sample as determined by means of the transport measurements presented in the main text, we also probed the shift ∆ f of the resonance frequency fres of the NMR circuit at temperatures across the supercon- ducting transition and magnetic...

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    10, we compare the 1 /T1T data of our NMR sample [ x = 0 .766(1)] with results for Ba 1−xKxFe2As2 with different potassium contents from Hirano et al

    1/T1T of Ba 1−xKxF e2As2 In Fig. 10, we compare the 1 /T1T data of our NMR sample [ x = 0 .766(1)] with results for Ba 1−xKxFe2As2 with different potassium contents from Hirano et al. [35]. Clearly, the data for our sample fit very well into the systematic behavior of these data from literature. 0 1 02 03 04 05 06 07 001 2 3 4 T his work x = 0.766(1), 8 T...

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    Gapped behavior at high temperatures As mentioned in the main text, the temperature- dependent 1/T1T shows a monotonous increase with in- creasing temperatures above 25 K. A similar behavior has been reported, for example, for LaFeAsO 0.89F0.11 by Ishida et al. [41]. This dependence may be described by a gapped behavior, following an exponential form 1/T1...

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    12, we show the temperature dependence of 1/T1T for a field of 16 T and compare it to our specific- heat data recorded at the same field

    1/T1T and specific-heat data at 16 T In Fig. 12, we show the temperature dependence of 1/T1T for a field of 16 T and compare it to our specific- heat data recorded at the same field. The 1 /T1T data at 16 T reveal a similar pseudogap behavior as observed at 8 T, but at a slightly lower temperature of about 10.5 K, which also coincides with the onset tempe...

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Pith tools

Reviewed August 10, 2026 · model on record in the stance chip above.