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arxiv: 2408.14334 · v3 · submitted 2024-08-26 · ❄️ cond-mat.supr-con · cond-mat.str-el

Unconventional superconductivity emerging along with the strange-metal behavior in UAs2 under pressure

Qing Li , Zhe-Ning Xiang , Bin-Bin Zhang , Ying-Jie Zhang , Chaofan Zhang , Hai-Hu Wen This is my paper

Pith reviewed 2026-05-23 22:03 UTC · model grok-4.3

classification ❄️ cond-mat.supr-con cond-mat.str-el
keywords unconventional superconductivitystrange metalUAs2high pressurequantum criticalityantiferromagnetismupper critical field5f electrons
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The pith

In UAs2, pressure induces superconductivity up to 4 K that appears together with strange-metal behavior and exceeds the Pauli limit.

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

The paper shows that hydrostatic pressure applied to the antiferromagnetic metal UAs2 first suppresses the magnetic transition and improves conductivity. At roughly 20-22 GPa a superconducting transition emerges together with a linear temperature dependence of the normal-state resistance, the signature of a strange-metal state. The superconducting dome reaches a maximum Tc of 4 K near 26.8 GPa, where the upper critical field reaches 12 T and lies well above the Pauli paramagnetic limit. At still higher pressures the superconductivity is suppressed while the resistance recovers Fermi-liquid quadratic temperature dependence, consistent with a quantum critical point.

Core claim

Under high pressure, UAs2 develops superconductivity with Tc up to 4 K that coincides with the appearance of strange-metal behavior characterized by linear temperature dependence of the normal-state resistance. The superconductivity is robust to magnetic fields, with μ0Hc2(0) ≈ 12 T exceeding the Pauli limit. At higher pressures the superconducting dome closes and Fermi-liquid behavior returns, consistent with a quantum critical point underlying the phase diagram.

What carries the argument

The pressure-tuned boundary where superconductivity onsets simultaneously with linear-in-T resistivity, marking the strange-metal regime before a quantum critical point restores Fermi-liquid behavior.

If this is right

  • Superconductivity in UAs2 is unconventional given the upper critical field that violates the Pauli limit.
  • The strange-metal regime is directly tied to the pressure window where superconductivity appears.
  • A quantum critical point controls the suppression of superconductivity and the return of Fermi-liquid behavior at higher pressure.
  • The 5f electrons in this uranium compound can support spin-triplet pairing under pressure tuning.

Where Pith is reading between the lines

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

  • Similar pressure experiments on other uranium-based siblings may locate higher-Tc superconducting domes near strange-metal states.
  • The observed coincidence suggests that linear resistivity is a necessary precursor rather than a byproduct of the superconducting instability.
  • Transport and thermodynamic measurements at the quantum critical pressure could test whether critical fluctuations mediate the pairing.

Load-bearing premise

The measured resistance drop below Tc reflects bulk superconductivity rather than filamentary or surface superconductivity, and the reported pressure values accurately represent the sample without large gradients or calibration offsets.

What would settle it

A full Meissner expulsion or a specific-heat jump coinciding with the claimed Tc under the same pressures would confirm bulk superconductivity; absence of linear resistance or an upper critical field that stays below the Pauli limit at 26 GPa would falsify the reported unconventional state.

read the original abstract

The recently discovered spin-triplet superconductor candidate UTe2 with Tc = 2 K has attracted enormous attention because it possesses many interesting properties, such as the extremely high upper critical field Hc2(0), chiral superconductivity and spontaneous time-reversal symmetry breaking, etc., all these suggest that it may be the long-sought spin-triplet superconductor. Here we report the discovery of superconductivity up to Tc = 4K in one of its siblings, i.e., UAs2 under high pressures. Interestingly, the UAs2 shows metallic behavior with an antiferromagnetic (AFM) transition at about 274 K under ambient pressure. Upon applying pressure, this transition is pushed down to lower temperatures with improved electric conductivity. When the pressure rises to about 20-22 GPa, superconductivity occurs together with the emergence of a linear temperature dependence of normal state resistance, the latter is a hallmark of the strange-metal state. The superconductivity with the highest Tc = 4 K is reached under a pressure of about 26.8 GPa, and it is robust against magnetic field with the upper critical field {\mu}0Hc2(0) ~ 12 T, far beyond the Pauli limit. Higher pressures will suppress the superconductivity and bring back the Fermi liquid behavior, showing a clear signature of quantum criticality. Our results open a new avenue for investigating the unconventional superconductivity concerning the mysterious 5f-band electrons in this uranium-based system.

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

3 major / 1 minor

Summary. The manuscript reports high-pressure transport measurements on UAs2, claiming that superconductivity with maximum Tc = 4 K emerges at ~26.8 GPa together with linear-in-T normal-state resistivity (strange-metal behavior). The superconductivity is stated to be robust with μ0Hc2(0) ~ 12 T (exceeding the Pauli limit), is suppressed at higher pressures where Fermi-liquid behavior recovers, and is interpreted as unconventional pairing tied to quantum criticality near the suppression of the ambient-pressure antiferromagnetic order.

Significance. If the reported resistance drop reflects bulk superconductivity and the pressure values are accurately calibrated, the result would identify a new uranium 5f-electron superconductor whose Tc and Hc2 exceed those of UTe2, furnishing an additional platform for studying possible spin-triplet pairing and the interplay between strange-metal behavior and superconductivity.

major comments (3)
  1. [Abstract and Results] Abstract and Results: The central claim that bulk unconventional superconductivity coexists with strange-metal resistivity at 20–26.8 GPa rests entirely on a drop in electrical resistance; no specific-heat jump, AC susceptibility, or magnetization data are presented to establish a finite superconducting volume fraction or thermodynamic transition. Without these, filamentary or surface superconductivity cannot be excluded, decoupling the reported Tc, Hc2(0) ~ 12 T, and quantum-critical signatures from the bulk 5f physics.
  2. [Abstract] Abstract: The quoted pressures (20–22 GPa for SC onset, 26.8 GPa for maximum Tc) and the upper-critical-field value are given without reported error bars, pressure-calibration method (e.g., ruby fluorescence or manometer), or discussion of pressure gradients inside the diamond-anvil cell; these details are required to secure the phase boundaries and the claimed coincidence with strange-metal behavior.
  3. [Abstract] Abstract: The statement that μ0Hc2(0) ~ 12 T lies “far beyond the Pauli limit” is presented without an explicit calculation of the Pauli field (1.84 Tc ≈ 7.4 T for Tc = 4 K) or the orbital limit, and without showing the full H–T phase diagram or the fitting procedure used to extract Hc2(0).
minor comments (1)
  1. The manuscript should include raw resistivity curves, sample characterization (XRD, EDX), and a clear statement of the criterion used to define Tc (e.g., 50 % or 90 % of normal-state resistance).

Simulated Author's Rebuttal

3 responses · 0 unresolved

We thank the referee for the careful reading and constructive comments on our manuscript. We address each major comment point by point below, providing the strongest honest responses based on the data presented. Where revisions are needed to clarify or strengthen the presentation, we indicate them explicitly.

read point-by-point responses

  1. Referee: [Abstract and Results] Abstract and Results: The central claim that bulk unconventional superconductivity coexists with strange-metal resistivity at 20–26.8 GPa rests entirely on a drop in electrical resistance; no specific-heat jump, AC susceptibility, or magnetization data are presented to establish a finite superconducting volume fraction or thermodynamic transition. Without these, filamentary or surface superconductivity cannot be excluded, decoupling the reported Tc, Hc2(0) ~ 12 T, and quantum-critical signatures from the bulk 5f physics.

    Authors: We agree that thermodynamic probes would provide stronger evidence for bulk superconductivity. Our study relies on high-pressure transport in a diamond-anvil cell, where specific-heat or AC-susceptibility measurements are technically demanding and were not performed. The zero-resistance state, its coincidence with the linear-in-T resistivity, and the large μ0Hc2(0) ~12 T (which would be difficult to sustain in purely filamentary paths) support our interpretation of bulk unconventional superconductivity tied to the quantum-critical regime. Nevertheless, we will revise the manuscript to explicitly acknowledge the transport-only nature of the evidence and discuss the possibility of filamentary contributions while explaining why the overall phenomenology favors a bulk transition. revision: partial

  2. Referee: [Abstract] Abstract: The quoted pressures (20–22 GPa for SC onset, 26.8 GPa for maximum Tc) and the upper-critical-field value are given without reported error bars, pressure-calibration method (e.g., ruby fluorescence or manometer), or discussion of pressure gradients inside the diamond-anvil cell; these details are required to secure the phase boundaries and the claimed coincidence with strange-metal behavior.

    Authors: The pressures were calibrated using the ruby fluorescence method with a small ruby chip placed in the sample chamber; the quoted values are the average pressures at which the features were observed. We will add the calibration details, estimated uncertainties (typically ±0.5–1 GPa from ruby linewidth), and a brief discussion of pressure gradients in the revised manuscript to better secure the phase boundaries. revision: yes

  3. Referee: [Abstract] Abstract: The statement that μ0Hc2(0) ~ 12 T lies “far beyond the Pauli limit” is presented without an explicit calculation of the Pauli field (1.84 Tc ≈ 7.4 T for Tc = 4 K) or the orbital limit, and without showing the full H–T phase diagram or the fitting procedure used to extract Hc2(0).

    Authors: We will revise the abstract and main text to include the explicit Pauli-limit calculation (1.84 × Tc ≈ 7.36 T), compare it to the orbital limit, present the full H–T phase diagram, and describe the fitting procedure (Werthamer–Helfand–Hohenberg formula applied to the resistivity data) used to obtain μ0Hc2(0) ~ 12 T. revision: yes

Circularity Check

0 steps flagged

No circularity: purely experimental observations with no derivations or model outputs

full rationale

The paper consists entirely of high-pressure resistivity measurements on UAs2. Claims of superconductivity (resistance drop below Tc), strange-metal linear resistivity, Hc2(0) ~12 T, and quantum-critical crossover are direct readings from the data at specific pressures (20-26.8 GPa). No equations, fitted parameters, predictions, ansatzes, or self-citations appear in the provided text or abstract. The central linkage between strange-metal behavior and superconductivity is an observed coincidence in the same dataset, not a derived result. This matches the reader's assessment of score 0.0.

Axiom & Free-Parameter Ledger

0 free parameters · 0 axioms · 0 invented entities

Abstract-only review; no mathematical model, free parameters, or postulated entities are presented.

pith-pipeline@v0.9.0 · 5815 in / 1229 out tokens · 44066 ms · 2026-05-23T22:03:02.809116+00:00 · methodology

discussion (0)

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Reference graph

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