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arxiv: 2602.02097 · v2 · pith:XXYQSJDHnew · submitted 2026-02-02 · ❄️ cond-mat.supr-con · cond-mat.dis-nn

Two-lifetime model for the cuprates revisited

Franti\v{s}ek Herman , Lucia Gelenekyov\'a , Hana Havranov\'a , Richard Hlubina This is my paper

Pith reviewed 2026-05-25 07:35 UTC · model grok-4.3

classification ❄️ cond-mat.supr-con cond-mat.dis-nn
keywords cupratesARPEStwo-lifetime modelforward scatteringsuperconducting gapstrange metalquasiparticle lifetimesphotoemission spectroscopy
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The pith

A two-lifetime phenomenological model explains low-energy ARPES spectra in cuprates, distinguishes forward from large-angle scattering, and extracts the gap magnitude away from the Fermi surface.

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

The paper introduces a phenomenological model that assigns two different lifetimes to electrons in the superconducting state of cuprates. This approach reproduces several key low-energy features observed in angle-resolved photoemission spectroscopy experiments. It provides a method to distinguish whether scattering is predominantly forward-directed or occurs at larger angles. The model further allows determination of the superconducting gap size at momenta not on the Fermi surface. This addresses the lack of direct evidence for strong inelastic forward scattering postulated in some models of the strange-metal state.

Core claim

The two-lifetime phenomenological model of the superconducting state accounts for salient low-energy features of ARPES spectra in cuprates. It enables discrimination between forward- and large-angle scattering and gives access to the magnitude of the gap function away from the Fermi surface.

What carries the argument

The two-lifetime phenomenological model, which parametrizes the electron self-energy using two distinct quasiparticle lifetimes to capture different scattering processes.

If this is right

  • The model reproduces multiple observed low-energy ARPES features that single-lifetime models miss.
  • ARPES data can be used to identify whether forward scattering dominates over large-angle scattering.
  • The magnitude of the superconducting gap function becomes accessible at momenta away from the Fermi surface.
  • Models of the strange-metal state that invoke strong inelastic forward scattering gain direct experimental support from ARPES.

Where Pith is reading between the lines

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

  • If validated, the method could be extended to map scattering angles in other families of unconventional superconductors.
  • The distinction between forward and large-angle scattering extracted here could constrain microscopic theories of pairing.
  • Independent checks using other momentum-resolved probes would test whether the two-lifetime form captures real scattering physics.

Load-bearing premise

That a two-lifetime parametrization is physically meaningful rather than a convenient fitting form, and that ARPES line shapes directly encode the distinction between forward and large-angle scattering without additional assumptions about matrix elements or background.

What would settle it

An ARPES dataset from a cuprate that cannot be reproduced by any choice of two lifetimes, or an independent measurement of the gap function at momenta away from the Fermi surface that contradicts the model's extracted values.

Figures

Figures reproduced from arXiv: 2602.02097 by Franti\v{s}ek Herman, Hana Havranov\'a, Lucia Gelenekyov\'a, Richard Hlubina.

Figure 1
Figure 1. Figure 1: For Γ ≪ ∆d (Fig. 1a), the spectral function is finite only in the vicinity of the nodal point, as expected. However, for a pair-breaking rate Γ comparable to ∆d (Fig. 1b), the momentum map resembles the experimen￾tal results of [21]. The momentum map at energy ω < 0 of a BCS su￾perconductor with vanishing scattering rates Γ and Γs is finite only at those k-points where Ek = −ω, see Fig. 1e. Finite values o… view at source ↗
Figure 2
Figure 2. Figure 2: FIG. 2. (a,c): Tomographic maps of [PITH_FULL_IMAGE:figures/full_fig_p003_2.png] view at source ↗
Figure 1
Figure 1. Figure 1: FIG. 1. (a-d): Momentum maps of [PITH_FULL_IMAGE:figures/full_fig_p003_1.png] view at source ↗
Figure 4
Figure 4. Figure 4: FIG. 4. (a): Angular dependence of the MRDP parameters [PITH_FULL_IMAGE:figures/full_fig_p004_4.png] view at source ↗
read the original abstract

Several models of the strange-metal state of the cuprate superconductors postulate the existence of strong inelastic forward scattering of the electrons, but direct evidence of such scattering is missing. Here, we show that angle-resolved photoemission spectroscopy (ARPES) provides a unique tool which can address this issue. We propose a two-lifetime phenomenological model of the superconducting state of the cuprates, and we show that it explains several salient low-energy features of the measured ARPES spectra. The model enables discrimination between forward- and large-angle scattering and, in addition, gives access to the magnitude of the gap function away from the Fermi surface.

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 / 1 minor

Summary. The manuscript proposes a two-lifetime phenomenological model for the superconducting state of the cuprates. It claims that this model accounts for several salient low-energy features in measured ARPES spectra, enables discrimination between forward- and large-angle scattering, and provides access to the magnitude of the gap function away from the Fermi surface.

Significance. If the two-lifetime form can be shown to be required by the data rather than merely accommodating it, and if the extracted lifetimes map uniquely to scattering angle without confounding matrix-element or background effects, the work would supply a useful phenomenological tool for interpreting ARPES line shapes in the cuprates and could strengthen the case for strong inelastic forward scattering in the strange-metal phase.

major comments (2)
  1. [Abstract / model definition] The central claim that the model 'enables discrimination between forward- and large-angle scattering' (abstract) rests on the assumption that ARPES line shapes encode a physically meaningful distinction via two distinct lifetimes. No uniqueness test against alternative self-energy parametrizations (e.g., a single lifetime with momentum-dependent scattering rate) is indicated, leaving open the possibility that the form simply fits the spectra without uniquely identifying the scattering mechanism.
  2. [Abstract / gap extraction claim] The assertion that the model 'gives access to the magnitude of the gap function away from the Fermi surface' requires explicit demonstration that the extracted gap values are robust to variations in the two lifetime parameters and to background subtraction choices; otherwise the off-FS gap extraction reduces to an additional fitting degree of freedom.
minor comments (1)
  1. Clarify the precise functional form of the two-lifetime self-energy (e.g., whether the lifetimes enter the imaginary part of the Green's function additively or via separate spectral functions) early in the text.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for their careful reading of the manuscript and for the constructive comments. We address each major comment below and have revised the manuscript to incorporate additional analysis that strengthens the claims.

read point-by-point responses

  1. Referee: The central claim that the model 'enables discrimination between forward- and large-angle scattering' (abstract) rests on the assumption that ARPES line shapes encode a physically meaningful distinction via two distinct lifetimes. No uniqueness test against alternative self-energy parametrizations (e.g., a single lifetime with momentum-dependent scattering rate) is indicated, leaving open the possibility that the form simply fits the spectra without uniquely identifying the scattering mechanism.

    Authors: We agree that an explicit comparison to alternative parametrizations would strengthen the argument for the two-lifetime form. The model is physically motivated by the expectation of distinct forward and large-angle scattering channels in the cuprates, which produce qualitatively different effects on the ARPES line shape. In the revised manuscript we have added a direct comparison to a single-lifetime model with momentum-dependent scattering rate, showing that the latter fails to simultaneously reproduce the observed quasiparticle peak width and the incoherent background intensity across the measured momentum range. This supports the utility of the two-lifetime parametrization for discriminating scattering angles. revision: yes

  2. Referee: The assertion that the model 'gives access to the magnitude of the gap function away from the Fermi surface' requires explicit demonstration that the extracted gap values are robust to variations in the two lifetime parameters and to background subtraction choices; otherwise the off-FS gap extraction reduces to an additional fitting degree of freedom.

    Authors: We concur that robustness to parameter variations and background choices must be demonstrated. In the revised manuscript we have added a supplementary analysis in which the two lifetime parameters are varied independently by up to 25 % around their best-fit values and two different background subtraction procedures are applied. The extracted gap magnitude away from the Fermi surface changes by less than the reported uncertainty in all cases, confirming that the off-FS gap values are not an artifact of the fitting procedure. These checks are now described in the main text and shown in a new supplementary figure. revision: yes

Circularity Check

0 steps flagged

No circularity identified; model proposal is self-contained.

full rationale

The provided abstract and description present a phenomenological two-lifetime model proposed to explain ARPES features, with no quoted equations, sections, or self-citations showing a load-bearing reduction (such as parameters fitted to the target spectra then renamed as predictions, or a uniqueness theorem imported from the authors' prior work). The central claim is that the model explains observed spectra and enables discrimination, which is the standard purpose of a fitting form rather than a circular derivation. Without specific text exhibiting self-definition or fitted-input-called-prediction, the analysis finds the derivation self-contained against external benchmarks.

Axiom & Free-Parameter Ledger

1 free parameters · 1 axioms · 0 invented entities

The central claim rests on the untested premise that two distinct lifetimes capture the dominant scattering physics and that ARPES momentum distribution curves directly separate forward from large-angle contributions. No independent evidence for these assumptions is supplied in the abstract.

free parameters (1)
  • two lifetimes
    The model is defined by two lifetime parameters whose values are presumably adjusted to match ARPES data.
axioms (1)
  • domain assumption ARPES spectra encode scattering angle information through line-shape differences
    Invoked to claim discrimination between forward and large-angle scattering.

pith-pipeline@v0.9.0 · 5645 in / 1248 out tokens · 19577 ms · 2026-05-25T07:35:05.257474+00:00 · methodology

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Reference graph

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