{"id":"32715e8b-f5fd-4e8b-9697-a1c22182d0f8","arxiv_id":"2506.14077","paper_version":1,"verdict":"CONDITIONAL","confidence":"MODERATE","novelty_score":6.0,"correctness_risk":"medium","formal_verification":"none","parameter_count":2,"one_line_summary":"The normal state and the field-suppressed ground state of electron-doped SLCO are electronically nematic, with the nematic amplitude enhanced near Tc and increasing toward underdoping.","lead":"Thin films of the electron-doped superconductor Sr0.9La0.1CuO2 show an electronic nematic phase: their electrical resistance changes as the current direction is rotated, both in the normal state and in the regime of superconducting fluctuations. This is the first report of nematicity in an electron-doped cuprate, suggesting the phenomenon may be universal to high-temperature superconductors.","discovery_kind":"new_application","skeptic_critique":{"model":"deepseek-v4-flash","headline":"The central claim rests on the ARR cross-pattern yielding true ρ_T on an anisotropic film, but the paper's gold control only validates the isotropic case, leaving current-spreading artifacts in the quantitative extraction unresolved.","rationale":"The most load-bearing link is between the raw ARR measurements and the abstract's claim of spontaneous electronic nematicity. Everything downstream—director rotation, substrate pinning, doping dependence, and the field-suppressed ground state—uses the Δρ and α extracted by Eqs. (1)–(2). If those extractions are contaminated by current-spreading or geometric artifacts that appear only when the sample is anisotropic, the conclusion of electronic nematicity loses its quantitative foundation, even though the observed 180° oscillations may be real. The reader identified the same assumption, and I agree with that identification. The manuscript is internally coherent, and the gold control plus the 45° phase relation are good-faith checks, which is why I would not move the verdict to reject or unverified. However, because the paper relies on a prior derivation and does not demonstrate the anisotropic-sample inversion on an independent standard, the conditional verdict is appropriate: the central claim should be accepted only with additional validation of the ARR extraction on an anisotropic system, either by simulation or by an anisotropic control sample with known ρ(φ). The missing error bars and raw data are secondary reporting concerns; they do not by themselves identify a specific technical failure mode. The finite-element test proposed above would settle the central concern directly.","tokens_in":12185,"tokens_out":14054,"duration_ms":165152,"concrete_test":"Build a finite-element model (e.g., COMSOL or a resistor-network SPICE model) of the exact four-arm cross geometry used in Fig. 2a, with a homogeneous anisotropic conductivity tensor σ = [ρ0 I + Δρ R(α) diag(1,−1) R(−α)]^{-1}. Inject I_x=I_0 cosφ and I_y=I_0 sinφ through the corresponding contacts, compute V_x and V_y at the voltage contacts, and extract Δρ and α using Eqs. (1)–(2). Sweep Δρ/ρ from 0 to 10% and α from 0° to 90°, including the reported α=95.84°; also run a control with Δρ=0. If the extracted values deviate from the input by more than the reported N≈1.5% (or if a nonzero Δρ is extracted from the isotropic control), the ARR extraction is not quantitatively reliable and the central nematic claim is not established; if the inversion is exact, the concern is resolved.","verdict_should_be":"UNCHANGED","load_bearing_attack":"The claim that SLCO is electronically nematic is carried by the ARR result ρ(φ)=ρ+Δρ cos[2(φ−α)] and ρ_T(φ)=Δρ sin[2(φ−α)] (Eqs. 1–2). For these equations to give the bulk longitudinal and transverse resistivities, the current density at the center of the cross pattern must be uniform and its direction must be set exactly by the ratio I_y/I_x. If the film has a resistivity tensor with off-diagonal components—as any nematic film with director not aligned with the pattern axes does—the current streamlines in the cross are not necessarily parallel to the injected-current vector, and the measured V_x and V_y can contain a geometric mixing of longitudinal and transverse response with the same 180° periodicity. The gold-film control shows the method does not create anisotropy in an isotropic conductor, but it does not test the quantitative inversion of Δρ and α for an anisotropic sample. The observed 45° phase relation and the temperature dependence of the director reduce the space of simple linear-mixing artifacts, but they do not eliminate a temperature-dependent current-redistribution artifact. The key derivation is only cited to refs. 20 and 28, not shown or independently checked in this manuscript.","agreement_with_reader":"agree"},"referee_report":{"model":"deepseek-v4-flash","summary":"The manuscript reports angle-resolved resistivity (ARR) measurements on electron-doped infinite-layer Sr0.9La0.1CuO2 (SLCO) thin films grown on KTaO3(001) and GdScO3(110) substrates, claiming that the normal state is electronically nematic from room temperature down to the superconducting transition, that the superconducting-fluctuation state and the field-suppressed ground state are also nematic, and that the nematicity is electronic in origin because the nematic amplitude is nearly independent of the orthorhombic lattice distortion while the director is pinned by it. The paper also presents a doping series showing enhanced nematicity in underdoped films.","tokens_in":12338,"tokens_out":10471,"duration_ms":101957,"significance":"If correct, this would be the first observation of electronic nematicity in an electron-doped cuprate and would significantly strengthen the view that nematicity is a universal ingredient of high-temperature superconductivity. The paper uses a high-resolution ARR method with a useful gold-film control, a two-substrate comparison, and a field-suppression experiment to argue for an intrinsic electronic origin. The temperature-dependent rotation of the nematic director and the similarity of the doping dependence to hole-doped LSCO are potentially important. However, the manuscript's central quantitative claims currently rest on an unvalidated inversion for anisotropic samples and on fits without error bars, so the significance will be fully realized only after these issues are addressed.","major_comments":[{"comment":"","section":"Page 4, description of ARR method and Eqs. (1)-(2)"},{"comment":"","section":"Fig. 2a and gold-film control paragraph"},{"comment":"","section":"Figs. 3e, 3f and Figs. 5g-5h"},{"comment":"","section":"Methods A1-A2 and Fig. 3"}],"minor_comments":[{"comment":"","section":"Title and Abstract"},{"comment":"","section":"Eqs. (1)-(2)"},{"comment":"","section":"Page 8, extrinsic-factors paragraph"},{"comment":"","section":"Fig. 3c-3d"}],"recommendation":"major_revision","confidential_remarks":"The projection-formula inconsistency in the ARR analysis is a serious internal error as written, although it may be a typographical issue. If it is a typo, the authors should correct it and re-present the derivation; if it is not, the central results likely change. The lack of error bars is also a systematic weakness for a paper making a first-discovery claim. These points are fixable within the manuscript's scope, so I recommend major revision rather than rejection. The paper is within the scope of cond-mat.supr-con and would be of interest if the quantitative basis is strengthened."},"author_rebuttal":null,"desk_editor":{"model":"deepseek-v4-flash","letter":"The one thing you should know: this is the first report of electronic nematicity in an electron-doped cuprate, and the case is more convincing than the average first-report. The authors use their established ARR method on SLCO, and the data show 180°-periodic oscillations in both ρ(φ) and ρ_T(φ) with the expected 45° phase relation, fitted with the same amplitude and director. That internal consistency is real evidence, not just curve fitting. The temperature-dependent director shift rules out static disorder or contact misalignment, and the gold-film control shows the method does not fabricate anisotropy in an isotropic metal. The substrate comparison is the paper's strongest card: on orthorhombic GSO the director is pinned to the lattice, on tetragonal KTO it is not, yet the nematic amplitude is nearly the same – that is a clean argument for an electronic origin. The field-suppression experiment, showing the same normal-state nematicity below Tc, is a nice addition that hole-doped cuprates do not easily allow.\n\nThe soft spots are real but not fatal. There are no error bars and no raw data, only a 'upon request' statement that will not fly in 2026. The ARR inversion equations are cited to prior work, not derived, and the gold control validates only the isotropic case; a skeptic can still worry about current-spreading artifacts in the anisotropic extraction. That said, the simultaneous fitting of both channels with shared parameters, plus the director's temperature dependence, makes a trivial geometric artifact unlikely. A referee should check the cited derivation and ask for error bars, but the central claim holds up under the evidence shown. The broad leap from two cuprate families to 'intrinsic to high-temperature superconductors' is an overreach worth softening, and the sample statistics are thin (one film per substrate for the main comparison).\n\nThis deserves a serious referee. The result, if correct, closes a long-standing gap and constrains theories of cuprate nematicity. I would bring it to our reading group and would cite it. Send it to peer review with a request for raw data and uncertainties.","headline":"First credible case for electronic nematicity in an electron-doped cuprate, built on a known method and controlled by a substrate comparison; the main gaps are missing error bars and a cited, not shown, quantitative inversion.","tokens_in":12961,"tokens_out":1946,"would_cite":true,"duration_ms":23597,"reading_group":"yes","serious_thinker":"yes","would_accept_peer_review":true},"rs_alignment":null,"lean_confirmation":null,"pith_extraction":{"msc":[],"pacs":[],"model":"deepseek-v4-flash","headline":"An electron-doped cuprate superconductor spontaneously breaks in-plane rotational symmetry in both its normal state and its field-suppressed zero-temperature ground state, showing electronic nematicity is intrinsic to high-temperature…","keywords":["electronic nematicity","electron-doped cuprates","Sr0.9La0.1CuO2","angle-resolved resistivity","high-temperature superconductivity","superconducting fluctuations","infinite-layer cuprates"],"falsifier":"Fabricate the same SLCO/KTO film into several independent ARR devices with different cross-arm widths, contact sizes, and current paths, and also measure a fixed-angle multi-Hall-bar device on the same area; if the extracted nematic amplitude $\\Delta\\rho$ and director $\\alpha$ vary with geometry or disagree between methods, the angular oscillations reflect a measurement artifact rather than a bulk electronic nematicity.","tokens_in":11922,"feed_emoji":"⚡","tokens_out":15274,"duration_ms":131297,"temperature":0.7,"pith_summary":"High-temperature cuprate superconductors can be doped with holes or electrons, and the two families differ in many ways: electron-doped cuprates lack the pseudogap, have different crystal structures, and host carriers with different orbital character. This paper aims to show that despite those differences, the electron-doped infinite-layer cuprate Sr$_{0.9}$La$_{0.1}$CuO$_2$ (SLCO) is electronically nematic—it spontaneously picks out one in-plane direction—already in its normal state from room temperature down to its superconducting transition, and even in the zero-temperature ground state obtained when a magnetic field suppresses superconductivity. The authors report that the nematic amplitude is essentially unchanged whether the film is grown on a tetragonal or an orthorhombic substrate, while the nematic director follows the substrate strain only on the orthorhombic one, which they take as evidence that the order is driven by electron-electron correlations rather than by the lattice. The same nematic order strengthens when superconducting fluctuations appear near $T_c$ and grows further as the doping is lowered toward underdoping, matching the behavior seen in hole-doped La$_{2-x}$Sr$_x$CuO$_4$. The broader claim is that electronic nematicity is a generic property of high-temperature superconductors regardless of carrier type, a conclusion that would constrain theories of high-temperature superconductivity.","feed_headline":"Electron-doped cuprate is nematic in normal and ground states","feed_subtitle":"The measurement puts electron-doped cuprates in the same nematic class as hole-doped ones, signaling a common mechanism.","key_machinery":"The central mechanism is the angle-resolved resistivity (ARR) method, in which a four-terminal cross-shaped pattern rotates the current direction continuously within the CuO$_2$ plane by controlling the current components $I_x = I_0\\cos\\phi$ and $I_y = I_0\\sin\\phi$ and measuring both the longitudinal and transverse voltages at each angle. The resistivity tensor components are then fit to $\\rho(\\phi) = \\overline{\\rho} + \\Delta\\rho\\cos[2(\\phi-\\alpha)]$ and $\\rho_T(\\phi) = \\Delta\\rho\\sin[2(\\phi-\\alpha)]$, where the relative amplitude $N = \\Delta\\rho/\\overline{\\rho}$ quantifies the nematic strength and the phase $\\alpha$ locates the nematic director. The key work of this machinery is to map the full 360-degree angular dependence of both resistivities on one small, uniform region of the film, so that the measured oscillations can be separated from sample inhomogeneity and contact artifacts by their dependence on temperature, strain, and magnetic field.","core_discovery":"The paper's central discovery is that electronic nematicity—the spontaneous breaking of in-plane fourfold (C4) rotational symmetry down to twofold (C2) symmetry—exists in an electron-doped cuprate superconductor, Sr$_{0.9}$La$_{0.1}$CuO$_2$, and that it pervades both the normal state and the state reached when superconductivity is extinguished by a magnetic field. Using angle-resolved resistivity measurements with a cross-shaped device that rotates the current direction continuously, the authors find that the longitudinal resistivity oscillates as $\\overline{\\rho} + \\Delta\\rho\\cos[2(\\phi-\\alpha)]$ and the transverse resistivity as $\\Delta\\rho\\sin[2(\\phi-\\alpha)]$, giving a nematic amplitude $N = \\Delta\\rho/\\overline{\\rho}$ of about 1.5% at 300 K and a director $\\alpha$ that shifts with temperature and rotates abruptly near $T_c$. The nematic amplitude is not changed when the substrate is switched from tetragonal KTaO$_3$(001) (in-plane lattice orthorhombicity below 0.05%) to orthorhombic GdScO$_3$(110) (film orthorhombicity 0.38%), while the director is pinned by the orthorhombic strain; the authors take this near-independence of amplitude as proof that the nematicity is electronic in origin. When a magnetic field of up to 16 T suppresses superconductivity at low temperature, the normal-state nematic amplitude and director are recovered at all temperatures below $T_c$, so the zero-temperature ground state is nematic. The nematicity also grows as the effective doping is reduced from optimal to underdoped, closely paralleling the behavior previously reported in hole-doped LSCO.","pith_inferences":["A testable extension of the paper's logic is that the same angle-resolved resistivity signatures should appear in other electron-doped cuprates such as Nd$_{2-x}$Ce$_x$CuO$_4$, and the director rotation near $T_c$ should scale with the strength of superconducting fluctuations; if not, the universality claim would need revision.","The near-independence of the nematic amplitude from substrate orthorhombicity implies a large electronic nematic susceptibility. Measuring the response of $N$ to uniaxial stress, or to a magnetic field applied along different in-plane directions, could map this susceptibility tensor and help distinguish spin- and charge-driven mechanisms.","If the zero-temperature ground state is truly nematic, the superconducting state that develops from it should show a two-fold anisotropy in its upper critical field, vortex lattice, or fluctuation conductivity even in nominally tetragonal films—an observable the present transport data do not directly address."],"forward_implications":["Electronic nematicity is a common feature of both hole- and electron-doped cuprate superconductors, so carrier type, crystal structure, and the presence or absence of a pseudogap are not prerequisites for nematic order.","The zero-temperature ground state of optimally doped SLCO, once superconductivity is removed by a magnetic field, is nematic rather than a conventional isotropic Fermi liquid.","Superconducting fluctuations in SLCO are themselves nematic, with a distinct director orientation and strongly enhanced amplitude near $T_c$, so superconductivity appears to develop out of a nematic-fluctuating state.","The near-independence of the nematic amplitude from a large applied orthorhombic lattice distortion, together with the pinning of the director, implies that the nematic order is electronically driven and only weakly coupled to the lattice.","The nematic amplitude grows as the effective doping is reduced from optimal to underdoped, matching the doping dependence seen in hole-doped LSCO and indicating the order is intrinsic to the cuprate family."],"supporting_citations":[{"why":"The hole-doped LSCO nematicity result that this paper extends and compares against, and a source of the ARR equations.","marker":"[20]"},{"why":"The angle-resolved resistivity methodology paper that supplies the cross-pattern device design and the extraction equations used here.","marker":"[28]"},{"why":"Further establishes the ARR method and its application to cuprate transport, supporting the interpretation of transverse resistivity oscillations.","marker":"[22]"},{"why":"The SLCO thin-film synthesis recipe and Tc benchmark used to validate the quality of the films.","marker":"[29]"},{"why":"The doped-Mott-insulator framework for high-temperature superconductivity that motivates the comparison of hole and electron doping.","marker":"[1]"},{"why":"The reference review of electron-doped cuprates establishing the structural and electronic differences that this paper's nematicity claim addresses.","marker":"[2]"},{"why":"The theoretical definition of electronic nematicity in Fermi fluids that the paper adopts.","marker":"[10]"}],"fun_headline_variants":["Nematic order found in electron-doped cuprate superconductor","Electron-doped cuprate shows nematicity in normal and ground states","Nematicity intrinsic to cuprates, electron-doped now confirmed","Cuprate nematicity now includes electron-doped","Electron-doped cuprate is nematic across phases"],"cache_read_input_tokens":3200,"weakest_assumption_plain":"The paper assumes that the angle-resolved resistivity device measures the true bulk longitudinal and transverse resistivity of the film, meaning the current flow at the cross-shaped pattern is uniform enough that the measured voltages give the longitudinal and transverse components directly, without sizeable corrections from current spreading, contact misalignment, or geometric magnetoresistance.","fun_headline_variants_meta":{"raw":{"variants":["Nematic order found in electron-doped cuprate superconductor","Electron-doped cuprate shows nematicity in normal and ground states","Nematicity intrinsic to cuprates, electron-doped now confirmed","Cuprate nematicity now includes electron-doped","Electron-doped cuprate is nematic across phases"]},"model":"deepseek-v4-flash","effort":"low","cost_usd":0.000699,"raw_usage":{"total_tokens":3260,"prompt_tokens":1154,"completion_tokens":2106,"prompt_tokens_details":{"cached_tokens":384},"prompt_cache_hit_tokens":384,"prompt_cache_miss_tokens":770,"completion_tokens_details":{"reasoning_tokens":2018}},"tokens_in":770,"tokens_out":2106,"duration_ms":16940,"temperature":1.0,"reasoning_tokens":2018,"cache_read_input_tokens":384,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-08-07T00:17:56.242547+00:00","model_set":{"reader":"deepseek-v4-flash"},"falsifier":"Fabricate the same SLCO/KTO film into several independent ARR devices with different cross-arm widths, contact sizes, and current paths, and also measure a fixed-angle multi-Hall-bar device on the same area; if the extracted nematic amplitude $\\Delta\\rho$ and director $\\alpha$ vary with geometry or disagree between methods, the angular oscillations reflect a measurement artifact rather than a bulk electronic nematicity.","supporting_citations":[{"cited_title":"T., He, X","cited_arxiv_id":null,"evidence_quote":"The hole-doped LSCO nematicity result that this paper extends and compares against, and a source of the ARR equations."},{"cited_title":null,"cited_arxiv_id":null,"evidence_quote":"The angle-resolved resistivity methodology paper that supplies the cross-pattern device design and the extraction equations used here."},{"cited_title":null,"cited_arxiv_id":null,"evidence_quote":"Further establishes the ARR method and its application to cuprate transport, supporting the interpretation of transverse resistivity oscillations."},{"cited_title":null,"cited_arxiv_id":null,"evidence_quote":"The SLCO thin-film synthesis recipe and Tc benchmark used to validate the quality of the films."},{"cited_title":"A., Nagaosa, N","cited_arxiv_id":null,"evidence_quote":"The doped-Mott-insulator framework for high-temperature superconductivity that motivates the comparison of hole and electron doping."},{"cited_title":"P., Fournier, P","cited_arxiv_id":null,"evidence_quote":"The reference review of electron-doped cuprates establishing the structural and electronic differences that this paper's nematicity claim addresses."},{"cited_title":"A., Lawler, M","cited_arxiv_id":null,"evidence_quote":"The theoretical definition of electronic nematicity in Fermi fluids that the paper adopts."}],"review_version":1}