CuIr2Te4: A Quasi-Two-Dimensional Ternary Telluride Chalcogenide Superconductor

Dao-Xin Yao; Dong Yan; Guohua Wang; Hsin Lin; Huixia Luo; Jie Ma; Junjie Yin; Meng Wang; Shuang Jia; Tay-Rong Chang

REVIEW 2 major objections 6 minor 1 cited by

CuIr2Te4: A Quasi-Two-Dimensional Ternary Telluride Chalcogenide Superconductor

T0 review · 2 major / 6 minor · reviewed 2026-08-14 · deepseek-v4-flash

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Pith's one-line read CuIr2Te4 is the first AB2X4-type telluride superconductor, with a bulk critical temperature of 2.5 K and a charge-density-wave transition near 250 K.

desk verdict A credible new bulk superconductor at 2.5 K in a layered telluride, but the CDW claim in the title is not backed by the data they present. read the letter →

arxiv 1908.05438 v1 pith:5K3AT2XQ submitted 2019-08-15 cond-mat.supr-con

Dong Yan , Yijie Zeng , Guohua Wang , Yiyuan Liu , Junjie Yin , Tay-Rong Chang , Hsin Lin , Meng Wang

show 4 more authors

Jie Ma Shuang Jia Dao-Xin Yao Huixia Luo

This is my paper · ORCID

classification cond-mat.supr-con

keywords CuIr2Te4superconductivitychargedensitywaveAB2X4chalcogenideternarytelluridelayeredmaterialquasi-two-dimensionaliridium

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 reports that the layered ternary telluride CuIr2Te4 is a bulk superconductor with $T_c \approx 2.5$ K, and argues that a charge-density-wave (CDW) transition around 250 K coexists with the superconductivity. If correct, it is the first superconducting example in the AB2X4 telluride family and provides a quasi-two-dimensional platform for studying CDW–superconductivity competition. The claim matters because few AB2X4 chalcogenides superconduct at all, and none of the tellurides had previously been shown to do so. The authors establish the bulk nature of superconductivity through resistivity, magnetic susceptibility, and specific heat, and support the CDW assignment with a hysteresis anomaly in susceptibility and resistivity. They also use first-principles calculations to argue that the CDW is not driven by Fermi-surface nesting or a Kohn anomaly, leaving the microscopic origin of the 250 K transition open.

What carries the argument

The central object is the CuIr2Te4 crystal itself: a disordered trigonal structure (space group P-3m1, No. 164) composed of quasi-two-dimensional IrTe2 layers with copper ions occupying half the interlayer 1b sites. This structure gives the material its two-dimensional character and sets it apart from the cubic spinel AB2X4 superconductors. The argument is carried by a combination of bulk thermodynamic and transport probes—electrical resistivity, dc magnetization, and heat capacity—together with first-principles density-functional calculations. The calculations supply the orbital character of the bands near the Fermi energy, the absence of Fermi-surface nesting, and a phonon dispersion without a Kohn anomaly, and they reproduce the measured Debye temperature and low-temperature phonon heat capacity semi-quantitatively. That combined evidence is what lets the authors propose a CDW-bearing superconductor in which the CDW is not of the conventional nesting or Kohn-anomaly type.

What would settle it

Cooling a CuIr2Te4 crystal through 250 K while collecting electron or x-ray diffraction would settle the CDW question: a superlattice reflection or a periodic lattice distortion appearing at the anomaly, and vanishing above it, would confirm the CDW, while resistivity and magnetization anomalies with no structural signature would force a different assignment. A tunneling measurement of an electronic gap opening below 250 K would provide the same discrimination.

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Extended reading notes

Core claim

The central discovery is that polycrystalline CuIr2Te4, which crystallizes in a disordered trigonal P-3m1 structure made of two-dimensional IrTe2 layers with Cu intercalated between them, becomes superconducting below about 2.5 K. The transition is bulk: resistivity drops sharply, magnetization shows strong diamagnetism with a superconducting volume fraction near 96%, and specific heat shows a jump $\Delta C/\gamma T_c \approx 1.82$, above the standard weak-coupling value of 1.43. The same compound shows a hysteretic anomaly in resistivity and magnetization near 250 K, which the paper interprets as a CDW transition, following an earlier report on the same material. Electronic structure calculations show states near the Fermi level from Te $p$ and Ir $d$ orbitals, with no Fermi-surface nesting, and phonon calculations show no Kohn anomaly, indicating that the CDW, if present, does not have a conventional nesting or phonon-softening origin. This makes CuIr2Te4 the first reported AB2X4-type ternary telluride superconductor and a candidate system for studying coexistence of CDW and superconductivity in two dimensions.

Load-bearing premise

The load-bearing assumption is that the 250 K anomaly seen in resistivity and magnetization is actually a charge-density-wave transition, since the paper determines no CDW wave vector or superlattice and provides no microscopic image of the modulation; if that anomaly is instead a structural, magnetic, or other electronic transition, the coexistence claim weakens, while the 2.5 K superconductivity would remain.

Editorial extensions

If this is right

CuIr2Te4 is the first confirmed superconductor in the AB2X4 telluride family, extending a family that previously contained only sulfides and selenides.
The coexistence of bulk superconductivity at 2.5 K with a CDW-like transition at 250 K makes CuIr2Te4 a quasi-two-dimensional system in which the two ordered states can be studied in the same material.
The specific-heat jump of about $1.82\,\gamma T_c$ and the electron–phonon coupling near 0.65 place CuIr2Te4 in the moderate-coupling regime, so phonon-mediated pairing is a viable description.
The computed absence of Fermi-surface nesting and of a Kohn anomaly rules out the two most common CDW mechanisms, so the 250 K transition must have a different origin if it is a CDW.
The low upper critical field of about $\mu_0 H_{c2}(0) \approx 0.12$ T and the long coherence length of about 53 nm mean small magnetic fields fully suppress superconductivity, making CuIr2Te4 easy to probe across the transition.

Reading between the lines

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

A natural next experiment, not reported in the paper, is to apply pressure or alter the Cu concentration: in many CDW superconductors partial suppression of the CDW raises $T_c$, so a dome-shaped $T_c$ versus pressure or doping curve is a plausible outcome.
Because the Cu site is only half occupied, the interlayer Cu arrangement is disordered; ordered intercalation, or Cu off-stoichiometry, could change the interlayer Te–Te coupling and with it both the CDW temperature and $T_c$, a question best tested on single crystals.
The paper's negative results for nesting and Kohn anomaly point toward a local mechanism for the 250 K anomaly, so a structural probe such as x-ray diffuse scattering or scanning tunneling microscopy below 250 K could reveal a periodic lattice distortion even if the wave vector is not obvious from band structure.
The near-100% superconducting volume fraction and the lack of spin polarization make an extrinsic impurity origin for the 2.5 K transition unlikely, but the small Ir deficiency detected by composition analysis means the effect of Ir vacancies on $T_c$ could be tested by annealing or by preparing slightly Ir-rich samples.

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Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, and a circularity audit.

Desk Editor's Note

read the letter

Short version: the superconductivity discovery is real and worth knowing about; the CDW is a label on an anomaly that the paper itself admits is uncharacterized. Treat the two claims separately.

The genuinely new result is that CuIr2Te4, previously known only for a resistance anomaly down to 4.2 K, becomes superconducting. That is supported three independent ways: a sharp resistivity drop, diamagnetic shielding of about 96%, and a specific-heat jump with ΔC/γTc = 1.82. Basic characterization (XRD, EDXS, HRTEM) looks adequate, and the derived parameters (Hc1, Hc2, coherence length) come from standard analyses. This is a useful addition to the short list of AB2X4 superconductors and a plausible quasi-2D platform.

The soft spot is the CDW. The evidence is a resistivity and susceptibility anomaly around 250 K with hysteresis. There are no superlattice reflections, no structural modulation from diffraction or microscopy, and no microscopic image. The authors explicitly write that the CDW wave vector is unknown, and their own DFT shows no Kohn anomaly and no Fermi-surface nesting. That doesn't rule out a CDW, but it means the headline 'CDW-bearing superconductor' is not established. The anomaly could be structural, an order-disorder transition of the half-occupied Cu site, or something else. The paper would be more accurate if it said 'an unidentified transition near 250 K' and kept CDW as a tentative suggestion.

The DFT part is fine as context. The absence of nesting and Kohn anomaly is consistent with the authors' own conclusion that even if a CDW exists, it is not driven by those mechanisms. But it cannot validate the CDW assignment. The self-citation to Kang et al. is not a problem.

Who is this for? Experimental people hunting for new layered superconductors, and anyone interested in CDW/SC coexistence claims. It deserves serious refereeing because the superconducting discovery is solid and new. My recommendation: major revision. Ask the authors to either provide structural evidence for the CDW or reframe the paper around the superconductivity and explicitly downgrade the CDW to a tentative observation. As is, the central superconductivity claim holds; the coexistence narrative overreaches.

Referee Report

2 major / 6 minor

Summary. The manuscript reports the synthesis, structural characterization, and physical property measurements of polycrystalline CuIr2Te4, a layered ternary telluride with a disordered trigonal P-3m1 structure. The central claims are that CuIr2Te4 is a bulk superconductor with Tc ≈ 2.5 K, evidenced by a resistivity drop, a strong diamagnetic response with about 96% shielding, and a specific-heat anomaly at the same temperature, and that a charge-density-wave transition near 250 K coexists with the superconductivity, inferred from resistivity and magnetization anomalies. The authors supplement the experiments with DFT band-structure, Fermi-surface, and phonon calculations, and they extract superconducting parameters including λep ≈ 0.65, ΘD ≈ 185 K, N(EF) ≈ 2.72 states/eV f.u., and μ0Hc2(0) ≈ 0.12 T.

Significance. If the superconductivity claim alone stands, this is a useful new data point: a quasi-two-dimensional ternary telluride superconductor in the AB2X4 family, which has previously yielded only sulfo- and selenospinel superconductors. The superconducting evidence is genuinely multi-probe: resistivity, susceptibility with large shielding fraction, and a specific-heat jump with ΔC/γTc = 1.82 at the same temperature. The authors are also transparent about the main limitation, explicitly noting that the CDW superlattice wave vector is unknown. The broader novelty, however, depends on the CDW identification: the title, abstract, and conclusion present CuIr2Te4 as a 'CDW-bearing superconductor' and a platform for CDW-superconductivity interplay, and that framing is currently weaker than the superconductivity evidence. The manuscript does not ship code or machine-checked derivations; its contribution is experimental with supporting DFT.

major comments (2)

[Results and Discussion (Fig. 2c) and Conclusion] The identification of the 250 K anomaly as a charge-density wave is not established by the presented evidence. The only experimental indications are a resistivity anomaly and a magnetic susceptibility anomaly with hysteresis; no low-temperature diffraction, electron-diffraction superlattice reflections, or local probe image showing a periodic lattice modulation is provided. The manuscript itself states, 'Since the wave vector characterizing the CDW phase is not determined in our work, the superlattice corresponding to CDW is thus unknown.' Moreover, the DFT phonon calculation (Fig. 6) shows no Kohn anomaly and the Fermi surface (Fig. 5) is stated to have no remarkable nesting, so the theoretical section does not corroborate the CDW assignment. The anomaly could equally be a structural transition, a Cu order-disorder transition, or another electronic instability. Because the title, abstract, and conclusion present CuIr2Te4 as a 'CDW-bearing superconductor,' this is a load-bearing point. The authors should either supply direct structural evidence for a CDW superlattice or revise the manuscript to describe the 250 K feature as an anomaly of undetermined origin and remove the CDW-coexistence framing from the title and conclusion.
[Results and Discussion, heat capacity paragraph] The bulk-superconductivity claim would be easier to verify if the specific-heat anomaly were presented more explicitly. The text reports ΔC/γTc = 1.82 from data in Figure 3a, but the equal-area construction used to define Tc is only mentioned in the Experimental section and the way ΔC is separated from the phonon background at the transition is not described. Since the specific-heat jump is one of the three pillars of the bulk-superconductivity claim, the authors should show the raw Cp/T versus T data near the transition and describe the construction used to extract ΔC and Tc.

minor comments (6)

[Results and Discussion, McMillan analysis] The value of the Coulomb pseudopotential μ* used in the inverted McMillan formula is not stated; because λep = 0.65 depends on this choice, the assumed μ* should be reported.
[Table 2] Several cells in Table 2 are empty without explanation; the caption should indicate whether those entries are unavailable, not measured, or not applicable.
[Figure 1 caption] The caption contains a duplicated and truncated sentence: '(c) Selected area (100) direction. (b) HRTEM image...' The caption should be rewritten so that each panel is described once and completely.
[Abstract and crystallography] The space group is written as 'P3m1' in the abstract and elsewhere; the standard notation used in the text and tables is P-3m1 (No. 164). Please use a single consistent notation.
[Results and Discussion, susceptibility analysis] The discussion of spin susceptibility χs(q,iωn) mentions the correlation U but no calculated or assumed value of U is given; either provide the calculation or rephrase the statement as qualitative.
[Results and Discussion, lower critical field] The demagnetization factor is reported to lie in a wide range N = 0.1–0.592, but the quoted uncertainty in μ0Hc1(0) = 0.028(2) T appears to reflect only the least-squares fit; the propagation of the N uncertainty should be stated.

Circularity Check

0 steps flagged · score 0.0 of 10

No significant circularity: the superconducting and normal-state claims are read directly from measurements, and derived parameters are standard BCS/McMillan conversions rather than fitted inputs renamed as predictions.

full rationale

All load-bearing claims are read directly from measured data. The 2.5 K superconducting transition is established by three independent probes (resistivity, magnetic susceptibility, and specific heat), and the normalized specific-heat jump C/γTc = 1.82 is computed from measured Cp and γ with a standard BCS comparison. Derived parameters such as λep, N(EF), and ΘD are obtained from the inverted McMillan formula and the fitted γ and β values; none of these parameters is fed back to produce or predict Tc. The DFT band-structure and phonon calculations are compared with experiment semi-quantitatively and do not fix the experimental Tc. The CDW assignment is an interpretation of the 250 K anomaly in resistivity and magnetization; the paper explicitly states that the CDW wave vector and superlattice are unknown and that no Kohn anomaly or Fermi-surface nesting is found. That is an evidentiary or interpretation weakness, not circular reasoning: the label 'CDW' is not derived from itself, and no fitted parameter is renamed as a prediction. The self-citations (Refs. 22 and 49) serve as background or comparison material and are not load-bearing. No equation or fitted quantity reduces to its own input, so the derivation chain is self-contained.

Assumptions & free parameters 4 free parameters · 5 assumptions · 0 invented entities

The central claim of superconductivity at 2.5 K does not depend on any fitted parameter; it is read directly from resistivity, susceptibility, and heat capacity. The free parameters listed affect derived quantities such as λep, N(EF), and critical fields. The DFT model depends on an ordered-cell approximation to the actual 50 percent Cu occupancy, and the CDW argument relies on interpreting anomalies without a measured wave vector.

free parameters (4)

Coulomb pseudopotential μ* = not quoted (conventional 0.1 to 0.15 implied)
Required by the inverted McMillan formula used to obtain λep = 0.65 and hence the experimental N(EF); the chosen value affects these derived numbers.
Electronic specific heat coefficient γ = 10.57 mJ mol^-1 K^-2
Obtained by fitting Cp = γT + βT^3 to 3 T heat capacity data between 4 and 10 K; used to compute ΔC/γTc and N(EF).
Phonon specific heat coefficient β = 2.15 mJ mol^-1 K^-4
Obtained from the same fit; determines Debye temperature ΘD and λep.
Demagnetization factor N = 0.1 to 0.592
Inferred from M(H) slopes at 1.8, 2.0, and 2.2 K assuming perfect diamagnetism; used to correct μ0Hc1.

assumptions (5)

domain assumption The normal-state specific heat follows Cp = γT + βT^3 in the fit range 4 to 10 K.
Used to extract γ and β; a significant electronic or magnetic contribution would change λep and N(EF).
ad hoc to paper The disordered 50 percent Cu occupancy can be approximated by an ordered doubled cell with one Cu every two IrTe2 layers.
DFT model construction; the authors state this gives semi-quantitative agreement, but other Cu arrangements could alter the band structure and phonons.
domain assumption PBE-GGA DFT with SOC and the finite-displacement phonon supercell is sufficient for this Ir/Te compound.
Relies on standard approximate exchange-correlation; strong electron correlations, if present, could change N(EF) and the phonon conclusions.
domain assumption The inverted McMillan formula with a constant μ* describes electron-phonon coupling.
Derivation of λep from Tc and ΘD; this is not a first-principles prediction.
domain assumption The WHH dirty-limit expression applies for extrapolating μ0Hc2(0).
Used to estimate the upper critical field from the linear slope near Tc; the disorder level is not directly characterized.

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Cite this review

Pith. "Pith review of CuIr2Te4: A Quasi-Two-Dimensional Ternary Telluride Chalcogenide Superconductor." pith.science (2026). https://pith.science/paper/5K3AT2XQ

@misc{pith2026190805438,
  author       = {Pith},
  title        = {Pith review of: CuIr2Te4: A Quasi-Two-Dimensional Ternary Telluride Chalcogenide Superconductor},
  year         = {2026},
  howpublished = {\url{https://pith.science/paper/5K3AT2XQ}},
  note         = {Machine review of arXiv:1908.05438}
}

read the original abstract

Here we report the first observation of superconductivity in the AB2X4-type ternary telluride CuIr2Te4, which is synthesized by a solid-state method in an evacuated quartz jacket. It adopts a disordered trigonal structure with space group P3m1 (No. 164), which embodies a two-dimensional IrTe2 layers and intercalated by Cu between the layers. We use a combination of experimental and first principles calculation analysis to look insight into the structural and physical properties. CuIr2Te4 consistently exhibited a bulk superconductivity transition at 2.5 K in electrical resistivity, magnetic susceptibility and specific heat measurements. Resistivity and magnetization measurements suggest a charge density wave transition (TCDW = 250 K) coexists in CuIr2Te4, which further signify the coexistence of superconductivity and CDW in the ternary telluride chalcogenide CuIr2Te4. Our discovery of the new CDW-bearing superconductor CuIr2Te4 opens a door for experimental and theoretical studies of the interplay between CDW and superconductivity quantum state in the condensed matter field.

Figures

Figures reproduced from arXiv: 1908.05438 by the authors.

**Figure 6.** The calculated phonon dispersion of CuIr2Te4 [PITH_FULL_IMAGE:figures/full_fig_p025_6.png] view at source ↗

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Forward citations

Cited by 1 Pith paper

Reviewed papers in the Pith corpus that reference this work. Sorted by Pith novelty score. Full citation record

Superconductivity in the Ru-Doped CuIr2Te4 Telluride Chalcogenide
cond-mat.supr-con 2019-08 conditional novelty 5.0 of 10

Ru doping of the telluride CuIr2Te4 suppresses the charge density wave near x=0.03 and produces a superconducting dome with optimal Tc=2.79 K at x=0.05.

Reference graph

Works this paper leans on

2 extracted references · 2 canonical work pages · cited by 1 Pith paper

[1]

(1) Lotgering, F. K. On the ferrimagnetism of some sulphides and oxides. Philips Res. Rep. 1956, 11,

work page 1956
[190]

Metal-insulator tran-sition in thiospinel CuIr2S4

(2) Nagata, S.; Hagino, T.; Seki, Y .; Bitoh, T. Metal-insulator tran-sition in thiospinel CuIr2S4. Physica B 1994, 194, 1077-1078. (3) Radaelli, P. G.; Horibe, Y .; Gutmann, M. J.; Ishibashi, H.; Chen, C. H.; Ibberson, R. M.; Koyama, Y .; Hor, Y . S.; Kiryukhin, V .; Cheong, S. W. Formation of isomorphic Ir3+ and Ir4+ octamers and spin dimerization in th...

work page 1994

Pith tools

Reviewed August 14, 2026 · model on record in the stance chip above.

[1] [1]

(1) Lotgering, F. K. On the ferrimagnetism of some sulphides and oxides. Philips Res. Rep. 1956, 11,

work page 1956

[2] [190]

Metal-insulator tran-sition in thiospinel CuIr2S4

(2) Nagata, S.; Hagino, T.; Seki, Y .; Bitoh, T. Metal-insulator tran-sition in thiospinel CuIr2S4. Physica B 1994, 194, 1077-1078. (3) Radaelli, P. G.; Horibe, Y .; Gutmann, M. J.; Ishibashi, H.; Chen, C. H.; Ibberson, R. M.; Koyama, Y .; Hor, Y . S.; Kiryukhin, V .; Cheong, S. W. Formation of isomorphic Ir3+ and Ir4+ octamers and spin dimerization in th...

work page 1994