{"id":"3394be15-610b-4a3e-9108-1d5b030d2078","arxiv_id":"2411.11570","paper_version":2,"verdict":"CONDITIONAL","confidence":"MODERATE","novelty_score":8.0,"correctness_risk":"medium","formal_verification":"none","parameter_count":6,"one_line_summary":"A superconducting junction with crossed conventional and radial Rashba spin-orbit fields shows a Josephson supercurrent diode effect even when the magnet is magnetized along the current direction, due to spin precession in the magnetic barrier.","lead":"The authors predict a new Josephson diode effect in superconductor/ferromagnet/superconductor junctions when conventional and radial (chiral) spin-orbit fields are combined at the two interfaces. This effect could serve as a sensitive electrical probe of chiral spin textures in twisted van der Waals materials.","discovery_kind":"new_method","skeptic_critique":{"model":"deepseek-v4-flash","headline":"The USDE is not shown to require chiral (radial) SOC: the right-interface field in Eq. (S4) is exactly the opposite CR field rotated by θR, so the effect is a generic consequence of relative Rashba-orientation mismatch, not of radial spin texture.","rationale":"The paper's strongest claim is that the USDE is 'not possible for conventional spin-orbit fields' and is induced by chiral (radial) spin-orbit coupling. The load-bearing concern is that this exclusivity is false: the model's θR parameter, which interpolates between tangential and radial Rashba fields, is exactly a spin-space rotation of the opposite conventional Rashba field. A global spin rotation about z applied to the right electrode maps the pure-radial case (θR=π/2) onto a purely tangential rotated Rashba field, leaving the superconductors, ferromagnet, and out-of-plane magnetization unchanged. Therefore, a junction with two conventional Rashba interfaces whose relative orientation is rotated by 90° must produce the identical ΔIc. This directly contradicts the abstract's assertion that the effect is impossible for conventional spin-orbit fields. The proposed experimental signature as a probe of chiral spin textures is undermined because the observable cannot distinguish a radial field from a rotated tangential one. The underlying physics—nonreciprocity from spin precession—is plausible and supported by two complementary numerics, so the paper's core calculation is not invalidated, but the central claim's novelty and interpretation require major revision. The reader's weakest_assumption about disorder/dephasing is a different issue; our concern is more fundamental and is identified here as the single most load-bearing one. A concrete numerical test with a purely tangential rotated Rashba field would settle whether the effect is specific to radial SOC or generic to orientation mismatch; based on the unitary equivalence, it will show the latter.","tokens_in":25883,"tokens_out":25469,"duration_ms":257543,"concrete_test":"Re-run the vertical-junction calculation of Fig. 3 for θR=0.5π, but replace the right-interface SOC with a purely tangential Rashba field rotated by α=π/2 relative to the opposite left field, i.e., Ω_R = α(cosα ky − sinα kx, −sinα ky − cosα kx, 0). If the resulting ΔIc(Θ) exactly reproduces the θR=0.5π curve in Fig. 3(b), the claim that a radial (chiral) component is essential is falsified. More generally, scan α from 0 to π and check that ΔIc ≠ 0 for α ≠ 0 (mod π).","verdict_should_be":"CONDITIONAL","load_bearing_attack":"The central claim that the USDE is 'not possible for conventional spin-orbit fields' and is induced by chiral (radial) Rashba coupling is overstated. The interface field at z=d in Eq. (S4) is Ω_R = α[-sin(θR)kx - cos(θR)ky, cos(θR)kx - sin(θR)ky, 0], which equals R_z(θR)(-Ω_L) with Ω_L = α[ky, -kx, 0]. Thus the 'crossed tangential-radial' configuration is simply the conventional Rashba field at z=0 rotated in spin space by θR relative to its opposite orientation. A pure radial field (θR=π/2) is unitarily equivalent, via a global spin rotation about z in the right electrode, to a conventional tangential Rashba field rotated by π/2. Since a global spin rotation in the right half leaves the s-wave pairing, the chemical potential, and the out-of-plane magnetization invariant, the entire scattering problem and all observables are identical to a junction with two conventional Rashba interfaces whose relative in-plane orientation is θR. Consequently, any relative rotation α ≠ 0 of two conventional Rashba fields should produce the same nonreciprocity, contradicting the abstract's exclusivity claim. The proposed use of the USDE as a 'sensitive probe of chiral spin textures' is therefore not justified: the effect does not distinguish radial from rotated tangential Rashba coupling.","agreement_with_reader":"partial"},"referee_report":{"model":"deepseek-v4-flash","summary":"The manuscript studies superconductor/ferromagnet/superconductor Josephson junctions with a conventional Rashba spin-orbit field at one interface and a 'crossed' Rashba field (parameterized by an angle θR) at the other. Using BdG scattering theory with the Furusaki–Tsukada formula, and independently with tight-binding Kwant simulations, the authors find that the critical current becomes nonreciprocal (Ic+ ≠ |Ic−|) when the ferromagnetic barrier has an out-of-plane magnetization component. This 'unconventional supercurrent diode effect' (USDE) is attributed to spin precession in the ferromagnet rather than to finite Cooper-pair momentum, and the paper proposes the effect as a probe of chiral spin textures.","tokens_in":26250,"tokens_out":17885,"duration_ms":186441,"significance":"The numerical results are solid: the BdG calculations and the Kwant tight-binding simulations are mutually consistent, and the predicted symmetries (sign reversal of ΔIc under m_z reversal or θR sign flip, and the absence of an SDE for collinear Rashba fields) are verified. The spin-precession mechanism is a qualitatively new route to a Josephson diode, distinct from the conventional finite-momentum-pairing mechanism, and the reported efficiencies (up to ~60%) are sizable. However, the central claim that the effect is specifically due to chiral, radial Rashba coupling, and is 'not possible for conventional spin-orbit fields', is not supported by the model itself. The right-interface field in Eq. (S4) is exactly a rotated opposite conventional Rashba field, and Fig. S6 shows that the USDE depends only on the relative angle between the two Rashba fields, vanishing when they are collinear. The effect therefore appears to be a generic consequence of non-collinear interfacial spin-orbit fields, not a unique signature of a chiral radial texture. This overstatement in the abstract and conclusions undermines the proposed use as a 'sensitive probe of chiral spin textures'.","major_comments":[{"comment":"The right-interface spin-orbit field in Eq. (S4) is Ω_R = α[-sinθR kx - cosθR ky, cosθR kx - sinθR ky, 0], which is exactly R_z(θR)(-Ω_L) with Ω_L = α[ky, -kx, 0]. Thus the 'crossed (tangential and radial)' configuration is parametrically identical to a relative in-plane rotation of two conventional Rashba fields. At intermediate θR (e.g., θR=0.2π, as used in Figs. 2 and 3), the right-interface field has both tangential and radial components, i.e., it is a conventional Rashba field with a rotated orientation. The abstract's statement that the USDE is 'not possible for conventional spin-orbit fields' is therefore inconsistent with the authors' own model. Fig. S6 confirms this reading: ΔIc is a function of the relative angle ΔθR=θR_R-θL_R and vanishes on the diagonal ΔθR=0, regardless of the individual Rashba angles. The exclusivity claim in the abstract and the corresponding conclusion should be revised, or the authors should provide a specific observable that distinguishes a radial field from a rotated tangential one.","section":"Abstract and Eq. (S4)"},{"comment":"The spin-precession mechanism described in the 'Physical picture' section requires only a non-zero angle between the precessing spin and the spin-orbit field at the second interface. It does not invoke any property unique to a momentum-aligned (radial) spin texture; a rotated tangential Rashba field, such as the one generated by Eq. (S21) for any θR, produces the same asymmetry. The paper's claim that the USDE is a probe of chiral spin textures (abstract and conclusions) is therefore not justified by the presented mechanism. At minimum, the authors should demonstrate that the USDE can distinguish a radial texture from an arbitrary rotated Rashba field; in the absence of such a demonstration, the effect is best described as arising from non-collinear interfacial spin-orbit fields.","section":"Physical picture, Fig. 4"}],"minor_comments":[{"comment":"The title emphasizes 'chiral spin-orbit coupling', but the model uses standard linear Rashba-type coupling with an orientation angle. Since the effect appears to be generic to non-collinear spin-orbit fields, a more neutral title such as 'Nonreciprocal Josephson current from non-collinear Rashba interfaces' would be more accurate.","section":"Title"},{"comment":"Fig. S6 is a key result showing that the USDE depends on the relative Rashba angle and vanishes on the diagonal. This figure should be cited in the main text, as it directly addresses the physical origin of the effect and would help the reader assess the exclusivity claim.","section":"Fig. S6"},{"comment":"The sentence 'the SOC field at the z=d interface is aligned oppositely owing to hybridization' is not explained in the text; a brief comment or reference would clarify the sign convention of the Rashba fields at the two interfaces.","section":"Physical picture, first paragraph"},{"comment":"In the Furusaki–Tsukada formula, the placement of the denominator √(ω_n²+Δ0²) appears ambiguous (it is written after a fraction); a clearer typesetting would avoid confusion.","section":"Supplementary Material, Eq. (S22)"}],"recommendation":"major_revision","confidential_remarks":"The paper reports a genuine and reproducible numerical finding, but the framing substantially overstates its novelty: the effect is not specific to a chiral radial spin texture but to a relative misorientation of Rashba fields. This is a matter of interpretation and presentation, not a flaw in the core numerics. The authors should be asked to recalibrate the abstract, title, and conclusions, and to remove or carefully qualify the 'probe of chiral spin textures' proposal unless they can identify a way to distinguish radial from rotated tangential Rashba coupling. I do not see grounds for rejection, as the spin-precession mechanism for a Josephson diode with out-of-plane magnetization is a useful contribution."},"author_rebuttal":null,"desk_editor":{"model":"deepseek-v4-flash","letter":"Quick take: this is a competent and well-supported theory paper. The genuinely new piece is a Josephson diode mechanism that does not use finite Cooper-pair momentum: one tangential Rashba interface, one interface with a radial component in its spin-orbit field, and an out-of-plane magnetization collinear with the current together produce nonreciprocal critical currents through direction-dependent spin precession. The authors support this with two independent numerical implementations (continuum BdG/Furusaki-Tsukada and tight-binding Kwant), check the symmetries (ΔIc changes sign with m_z or θ_R flip, vanishes for uniform fields), and verify explicitly that the Fermi surfaces show no finite-momentum pairing. That is real evidence, and the spin-precession picture, although qualitative, makes symmetry predictions the numerics confirm.\n\nSoft spots, in order. The clean ballistic junction is load-bearing: the effect lives entirely in coherent spin precession through the ferromagnet, and the model has no disorder or spin-dephasing. The paper acknowledges the idealization but does not estimate how much dephasing kills the asymmetry. No code or data is released, so exact reproduction means reimplementation. The 'not possible for conventional spin-orbit fields' claim is worded too strongly: the right-interface field in Eq. (S4) is R_z(θ_R)(-Ω_L), a one-parameter rotation of the opposite tangential field, so for 0<θ_R<π/2 it is a mixture of tangential and radial, not a pure radial texture. What the effect really requires is a field with a radial component, which conventional Rashba cannot provide for a fixed k. The stress-test's 'equivalent conventional junction' argument does not land: a spin rotation localized to the right lead changes the interface boundary condition and is not a gauge symmetry of the full junction, and the θ_R=0 numerical comparison confirms that two purely tangential fields give no diode. Still, the 'sensitive probe of chiral spin textures' conclusion should be softened; the diode measures θ_R, an orientational parameter, not chirality per se.\n\nWho this is for: people working on Josephson diodes and superconducting spintronics. It deserves a serious referee, not a desk reject. The referee should ask for code/data and a disorder or spin-relaxation estimate. I would engage with it.","headline":"Solid theory paper with a genuinely new Josephson diode mechanism, well checked by two numerics; the 'chiral probe' language is oversold and the clean-junction premise deserves an explicit caveat.","tokens_in":26737,"tokens_out":11403,"would_cite":true,"duration_ms":131455,"reading_group":"maybe","serious_thinker":"yes","would_accept_peer_review":true},"rs_alignment":null,"lean_confirmation":null,"pith_extraction":{"msc":[],"pacs":["74.50.+r","74.45.+c","72.25.-b"],"model":"deepseek-v4-flash","headline":"Crossed conventional and radial Rashba spin-orbit fields in a superconductor/ferromagnet/superconductor junction make the critical supercurrent nonreciprocal for magnetization along the current, through spin precession rather than…","keywords":["unconventional supercurrent diode effect","Josephson diode","Rashba spin-orbit coupling","radial Rashba","chiral spin texture","spin precession","nonreciprocal supercurrent"],"falsifier":"Measure the critical currents in a clean superconductor/ferromagnet/superconductor junction that has one conventional and one radial Rashba interface, with the magnetization set exactly along the transport direction; the prediction is $I_c^+ \\neq |I_c^-|$, with the sign of $\\Delta I_c$ reversing when the magnetization is reversed, while a calculation that adds strong spin-flip scattering in the ferromagnet should show the nonreciprocity vanishing. If equal critical currents are observed in a clean junction of this geometry, the spin-precession claim is falsified.","tokens_in":25696,"feed_emoji":"🔀","tokens_out":15098,"duration_ms":169152,"temperature":0.7,"pith_summary":"The paper predicts an unconventional supercurrent diode effect in superconductor/ferromagnet/superconductor junctions whose two interfaces carry different Rashba spin-orbit fields: conventional Rashba coupling on one side and a momentum-aligned radial Rashba field on the other. In this geometry the maximum supercurrent carried in one direction differs from that carried in the opposite direction even when the ferromagnet's magnetization lies along the current, a setting where the standard Cooper-pair-momentum mechanism for a supercurrent diode does not operate. The authors attribute the nonreciprocity to spin precession inside the magnetic barrier: the first interface fixes the spin orientation, the barrier magnetization rotates it, and the second interface's radial field turns the resulting precession angle into a direction-dependent transmission probability. They argue the effect is sizable, tunable, and distinct from the conventional diode mechanism, and propose it as a sensitive probe of chiral spin textures.","feed_headline":"Josephson diode from spin precession, not pair momentum","feed_subtitle":"Crossed conventional and radial Rashba fields make left/right supercurrents unequal when the magnet points along the current.","key_machinery":"The load-bearing configuration is the crossed-Rashba interface pair: one superconductor/ferromagnet interface has a conventional Rashba field $\\hat{\\Omega} \\propto (k_y, -k_x, 0)$, while the other has a spin-orbit field with a radial Rashba component whose direction is set by a Rashba angle $\\theta_R$, as predicted for twisted van der Waals homobilayers. The physical mechanism is spin precession in the ferromagnetic barrier: the first interface polarizes electron spins in-plane, the out-of-plane magnetization $\\mathbf{m} \\parallel \\hat{z}$ makes those spins precess, and the angle between the arriving spin and the local spin-orbit field at the second interface determines the transmission probability $T \\propto \\cos^2(\\varphi/2)$. Because the precession angle is different for propagation parallel and antiparallel to the magnetization, the transmission — and hence the critical supercurrent — becomes direction dependent. The numerical results come from a Bogoljubov–de Gennes scattering treatment with delta-function interfacial spin-orbit fields, and current-phase relations are evaluated with the Furusaki–Tsukada formula.","core_discovery":"The central discovery is that a Josephson junction with an exchange-split ferromagnetic barrier and crossed interfacial spin-orbit fields — conventional Rashba at one interface and radial Rashba at the other — displays nonreciprocal critical currents, $I_c^+ \\neq |I_c^-|$, when the barrier magnetization is collinear with the transport direction. The effect, which the authors call the unconventional supercurrent diode effect (USDE), does not rely on the finite center-of-mass Cooper-pair momentum that drives conventional Rashba supercurrent diodes; the computed Fermi surfaces show no momentum shift. Instead, the mechanism is spin precession: electron spins polarized in-plane by the first interface precess about the out-of-plane barrier magnetization and reach the second interface with an angle-dependent transmission probability $T \\propto \\cos^2(\\varphi/2)$ that differs for propagation along versus against the magnetization. Reversing the magnetization or reversing the chirality of the radial Rashba field reverses the sign of $\\Delta I_c = I_c^+ - |I_c^-|$, and the effect already appears in a single transverse channel. The authors demonstrate the mechanism numerically in a vertical three-dimensional junction and in a two-dimensional lateral tight-binding junction.","pith_inferences":["If the spin-precession mechanism is correct, the magnitude of the effect should track the ferromagnet's spin-coherence length, so measuring the diode asymmetry in barriers of increasing thickness or disorder could double as a quantitative probe of spin dephasing in chiral van der Waals magnets.","Because radial Rashba coupling is controlled by the twist angle of van der Waals layers, the predicted dependence on the Rashba angle suggests the effect could serve as an in-situ readout of twist angle in a Josephson device.","The same crossed-Rashba spin-precession geometry should also produce direction-dependent transmission in the normal, non-superconducting state of the magnetic junction, which would offer a simpler transport signature to test the mechanism before superconducting contacts are added."],"forward_implications":["A supercurrent diode can be realized in a vertical superconductor/ferromagnet/superconductor junction with an out-of-plane magnetized barrier and crossed Rashba interfaces, without an in-plane magnetic field and without finite-momentum Cooper pairing.","Reversing either the out-of-plane magnetization or the chirality of the radial Rashba field flips the sign of $\\Delta I_c$, so the diode direction is switchable by magnetization reversal or by changing the chiral texture.","Because the nonreciprocity arises per transverse channel, the effect can be sizable in narrow junctions, unlike the conventional mechanism that needs a superposition of many channels with different $\\varphi_0$ shifts.","In the modeled parameter range the relative diode efficiency $|\\Delta I_c|/I_c(\\Theta=0)$ reaches beyond 20% for small radial Rashba coupling and up to roughly 60%, comparable to or larger than typical conventional supercurrent diode efficiencies.","The same spin-precession reading applies to lateral two-dimensional junctions, where the effect persists up to the half-metallic limit and is tied to current-reversing 0–π-like transitions."],"supporting_citations":[{"why":"It establishes the magnetoanisotropic Josephson effect from interfacial spin-orbit fields in S/F/S junctions, the modeling context and 0–π behavior that this paper extends to crossed Rashba fields.","marker":"[11]"},{"why":"It supplies the conventional supercurrent-diode phenomenology and 0–π-like transition signatures that the paper uses to distinguish the unconventional effect.","marker":"[28]"},{"why":"It gives the microscopic picture in which the conventional diode arises from many transverse channels with distinct $\\varphi_0$ shifts, the mechanism this paper contrasts with its single-channel spin-precession effect.","marker":"[29]"},{"why":"It links the conventional supercurrent diode to finite Cooper-pair momentum through phase-asymmetric Andreev spectra, the mechanism the paper argues is not at work here.","marker":"[30]"},{"why":"It provides a representative finite-momentum-pairing theory of the intrinsic superconducting diode against which the crossed-field route is framed.","marker":"[56]"},{"why":"It predicts radial Rashba spin-orbit fields in twisted van der Waals heterostructures, which is the chiral spin texture assumed at the second interface.","marker":"[94]"},{"why":"It supplies the Furusaki–Tsukada Green's-function method from which the numerical current-phase relations are computed.","marker":"[98]"},{"why":"It implements the tight-binding quantum transport code used for the lateral-junction demonstration.","marker":"[105]"}],"fun_headline_variants":["Spin precession drives Josephson diode in chiral Rashba junctions","Unconventional supercurrent diode from spin precession alone","Radial Rashba unlocks Josephson diode without pair momentum","Chiral spin-orbit makes Josephson current rectifying"],"cache_read_input_tokens":3200,"weakest_assumption_plain":"The effect requires that electron spins precess coherently through the ferromagnetic barrier: the model assumes a clean, disorder-free junction in which spins keep their orientation until they reach the second interface, so if spin relaxation in the magnetic layer destroys that precession, the direction-dependent transmission and the diode effect disappear.","fun_headline_variants_meta":{"raw":{"variants":["Spin precession drives Josephson diode in chiral Rashba junctions","Unconventional supercurrent diode from spin precession alone","Radial Rashba unlocks Josephson diode without pair momentum","Chiral spin-orbit makes Josephson current rectifying"]},"model":"deepseek-v4-flash","effort":"low","cost_usd":0.000659,"raw_usage":{"total_tokens":3003,"prompt_tokens":925,"completion_tokens":2078,"prompt_tokens_details":{"cached_tokens":384},"prompt_cache_hit_tokens":384,"prompt_cache_miss_tokens":541,"completion_tokens_details":{"reasoning_tokens":2010}},"tokens_in":541,"tokens_out":2078,"duration_ms":12903,"temperature":1.0,"reasoning_tokens":2010,"cache_read_input_tokens":384,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-08-12T18:22:19.798770+00:00","model_set":{"reader":"deepseek-v4-flash"},"falsifier":"Measure the critical currents in a clean superconductor/ferromagnet/superconductor junction that has one conventional and one radial Rashba interface, with the magnetization set exactly along the transport direction; the prediction is $I_c^+ \\neq |I_c^-|$, with the sign of $\\Delta I_c$ reversing when the magnetization is reversed, while a calculation that adds strong spin-flip scattering in the ferromagnet should show the nonreciprocity vanishing. If equal critical currents are observed in a clean junction of this geometry, the spin-precession claim is falsified.","supporting_citations":[{"cited_title":"Costa, C","cited_arxiv_id":null,"evidence_quote":"It supplies the conventional supercurrent-diode phenomenology and 0–π-like transition signatures that the paper uses to distinguish the unconventional effect."},{"cited_title":"Costa, J","cited_arxiv_id":null,"evidence_quote":"It gives the microscopic picture in which the conventional diode arises from many transverse channels with distinct $\\varphi_0$ shifts, the mechanism this paper contrasts with its single-channel spin-precession effect."},{"cited_title":"Frank, P","cited_arxiv_id":null,"evidence_quote":"It predicts radial Rashba spin-orbit fields in twisted van der Waals heterostructures, which is the chiral spin texture assumed at the second interface."},{"cited_title":"Furusaki and M","cited_arxiv_id":null,"evidence_quote":"It supplies the Furusaki–Tsukada Green's-function method from which the numerical current-phase relations are computed."}],"review_version":1}