{"id":"89a8a01e-4462-482f-8952-1192ef4ec2a6","arxiv_id":"2607.04398","paper_version":1,"verdict":"CONDITIONAL","confidence":"HIGH","novelty_score":6.5,"correctness_risk":"medium","formal_verification":"none","parameter_count":4,"one_line_summary":"Polarization switching in inversion-asymmetric ferroelectric Josephson junctions produces history-dependent asymmetric critical and retrapping currents, a magnetic-field-free pseudo-superconducting-diode effect.","lead":"A theoretical model shows that ferroelectric Josephson junctions can produce unequal critical supercurrents in opposite directions without magnetic fields, via polarization switching during current sweeps. This history-dependent 'pseudo-diode' effect offers a tunable route to nonreciprocal superconducting circuits.","discovery_kind":"new_application","skeptic_critique":{"model":"grok-4.5","headline":"The linear polarization correction (Eq. 2) is the load-bearing premise for η=θ̃, but its validity under switching voltages is untested.","rationale":"The Reader correctly isolates the linear polarization correction together with the small-P_0 requirement as the weakest load-bearing assumption. The coupled RCSJ–LKT numerics are internally consistent and the history dependence is clearly demonstrated, so there is no internal contradiction that would force a REJECT. Because the effect is defined by the linear map and vanishes outside the switching window, experimental or nonlinear-model verification remains necessary; the CONDITIONAL verdict is therefore unchanged. The concrete test above directly probes whether the headline efficiency formula survives once the linearization is relaxed, which is the single most decisive check.","tokens_in":13390,"tokens_out":581,"duration_ms":7362,"concrete_test":"Replace the linear factors (1-θ̃P) in Eqs. (5)–(6) by a nonlinear form motivated by tunneling, e.g. exp(-κ(1-θ̃P)) or (1-θ̃P+λP^2), re-run the A=2 zero-T current sweeps of Fig. 2 with the same parameters, and extract η. If |η-θ̃| exceeds ~20 % or the polarization no longer switches under the same voltage window, the quantitative claim η=θ̃ (and the robustness of the pseudo-SDE) is compromised.","verdict_should_be":"CONDITIONAL","load_bearing_attack":"The central claim that polarization switching produces |i_c^+|=1+θ̃ and |i_c^-|=1-θ̃ (hence η=θ̃) rests entirely on the linearized conductance/critical-current correction of Eq. (2): I=C_0 V̇+(1-θP)V/R_0+(1-θP)I_c sin ϕ. The authors themselves note that this linearization is kept valid only by deliberately choosing a modest P_0=0.1 μC cm^{-2} (smaller than typical perovskites/HfO2, comparable to CuInP2S6) and that larger P_0 deepens the double well and suppresses switching. Once the junction is resistive, the voltage that drives LKT switching is precisely the regime in which higher-order polarization corrections to the tunneling barrier (or nonlinear conductance) would appear; if those corrections become O(1), the simple mapping from P=±1 to critical currents 1±θ̃ fails and the diode efficiency is no longer equal to the asymmetry factor. The finite-T histograms and intermediate-branch dynamics inherit the same linear map. Thus the history-dependent nonreciprocity is a clean prediction only inside the linear-coupling window that the paper assumes rather than derives.","agreement_with_reader":"agree"},"referee_report":{"model":"grok-4.5","summary":"The manuscript proposes a magnetic-field-free pseudo-superconducting-diode effect in inversion-asymmetric ferroelectric Josephson junctions. Coupling a polarization-dependent RCSJ equation (Eq. 2) to Landau-Khalatnikov-Tani dynamics yields history-dependent asymmetric critical and retrapping currents under current sweeps once polarization switches; the diode efficiency equals the asymmetry factor \thetã. The nonreciprocity is absent without switching, is tunable by ferroelectric parameters and sweep protocol, and is argued to remain robust under thermal noise via stochastic simulations.","tokens_in":13736,"tokens_out":937,"duration_ms":30695,"significance":"If the modeled effect is realized, FE-JJs would offer an electrically programmable, magnetic-field-free platform for nonreciprocal superconducting transport, complementing existing SDE mechanisms that typically require broken time-reversal symmetry. The work supplies a concrete, falsifiable dynamical prediction (efficiency tracks \thetã and vanishes below the switching threshold) grounded in a Lagrangian derivation of the coupled equations (SM), Heun integration of the SDEs, and 1000-sweep histograms that incorporate fluctuation-dissipation noise. These elements make the proposal a useful theoretical benchmark for ongoing experiments on polarization-controlled supercurrents.","major_comments":[{"comment":"The central mapping |i_c^+|=1+\thetã, |i_c^-|=1-\thetã (hence \theta=\thetã) is obtained by construction from the linear polarization correction in Eq. (2). The authors deliberately adopt a modest P_0=0.1 µC cm^{-2} so that the linearization remains valid and note that larger P_0 deepens the double well and suppresses switching. However, the voltages that drive LKT switching are precisely the regime in which higher-order (e.g., exponential) corrections to the tunneling barrier become non-negligible. Without a quantitative estimate of the linear window or a brief nonlinear extension, it remains unclear whether \theta=\thetã survives outside the assumed parameter range; the finite-T histograms and intermediate-branch dynamics inherit the same linear map.","section":"Model, Eq. (2) and Nonreciprocity at zero temperature"},{"comment":"Finite-temperature results are presented up to T=1 K while the caption of Fig. 4 estimates T_c ≃ 0.5 K from a simple BCS relation using the chosen I_c R_0. The model keeps I_c fixed (explicitly noted as a simplification) and therefore produces unphysical supercurrents above T_c. Restricting the histograms and Fig. 5 to T ≪ T_c, or restoring a realistic I_c(T), is required before the claim of thermal robustness can be accepted.","section":"Thermal effects, Eq. (11) and Fig. 4 caption"}],"minor_comments":[{"comment":"Figure 2 caption contains a duplicated sentence describing the blue/red versus gray curves.","section":"Fig. 2 caption"},{"comment":"The abbreviation JDE is introduced for Josephson diode effect without prior definition; SDE is used consistently elsewhere.","section":"Introduction"},{"comment":"Table I lists physical values for α_{1,2} and γ_p with literature citations; a one-sentence justification that these remain appropriate for the chosen 2-nm barrier and CuInP_2S_6-like P_0 would help readers assess realism.","section":"Table I"},{"comment":"In the SM, the resonance features of Fig. S3 are interesting but appear only for an artificially lowered ferroelectric frequency; a brief remark on whether they remain accessible for the main-text parameters would avoid over-interpretation.","section":"SM, Resonance features"}],"recommendation":"major_revision","confidential_remarks":"The manuscript is a clean, self-contained theory proposal that fits the journal's scope. The two major points are fixable by additional discussion or restricted temperature range; I do not see evidence of over-claiming beyond the linear model the authors themselves flag. Self-citations to the authors' prior polarization-control work are appropriate and not excessive."},"author_rebuttal":null,"desk_editor":{"model":"grok-4.5","letter":"The punchline is simple: in an inversion-asymmetric ferroelectric Josephson junction, current-induced polarization switching during a sweep makes the critical currents unequal (|i_c^+|=1+θ̃, |i_c^-|=1-θ̃) because the junction sits in opposite polarization states on the two branches. That is the pseudo-SDE, and it vanishes if the polarization never flips. They get it from a polarization-dependent RCSJ equation coupled to LKT dynamics, derived via Lagrangian in the SM and integrated with Heun, including thermal noise with proper fluctuation-dissipation strengths.\n\nWhat is actually new is the nonequilibrium, history-dependent mechanism itself—not another equilibrium CPR asymmetry or magnetochiral term. The simulations are clear: I–V and I–P hysteresis, intermediate metastable resistive branches for deeper wells (A=4), rocking potentials, finite-T histograms from 1000 sweeps that keep the asymmetry, and even an extra superconducting pocket from premature thermal escape plus switching. Parameters are taken from literature ranges or chosen for numerical convenience (small P0 ~0.1 µC/cm² so the linear correction stays valid and switching is possible). Diode efficiency equals the asymmetry factor by construction once switching occurs. Self-citations to their prior FE-JJ work are appropriate; the broader SDE literature is covered.\n\nThe soft spot is real but exactly the one they flag: everything maps through the linearized (1-θP) factor in both Ic and resistance. They pick modest P0 (CuInP2S6-like) so the approximation holds and the double well is not too deep; larger P0 kills switching. Under the voltages that actually drive LKT switching, higher-order barrier corrections could appear and spoil η=θ̃. No experiment, no shipped code, so this remains a well-specified prediction inside that window. Minor: temperature dependence of Ic is ignored, and the cosϕ shift of the double well is kept but said to be negligible.\n\nThis is for people building or modeling nonreciprocal superconducting circuits who already care about FE-JJs or field-free diodes. The math and numerics are careful enough that a serious editor should send it to referees. I would bring it to reading group if we are doing Josephson devices that week, and I would cite the mechanism when discussing electrically programmable nonreciprocity.","headline":"Clean dynamical prediction of history-dependent pseudo-SDE from polarization switching in FE-JJs; solid numerics, rests on the linear coupling they deliberately keep small.","tokens_in":14352,"tokens_out":581,"would_cite":true,"duration_ms":14026,"reading_group":"maybe","serious_thinker":"yes","would_accept_peer_review":true},"rs_alignment":null,"lean_confirmation":null,"pith_extraction":{"msc":[],"pacs":[],"model":"grok-4.5","headline":"Ferroelectric polarization switching in an asymmetric Josephson junction produces unequal critical currents without a magnetic field.","keywords":["superconducting diode effect","ferroelectric Josephson junction","polarization switching","RCSJ model","Landau-Khalatnikov-Tani dynamics","nonreciprocal supercurrent","magnetic-field-free"],"falsifier":"Fabricate an inversion-asymmetric FE-JJ with small spontaneous polarization (e.g., CuInP2S6-like), sweep bias past the polarization-switching threshold, and check whether the measured critical currents reverse with polarization history and give diode efficiency equal to the designed asymmetry factor; if polarization never switches or the critical currents remain equal, the claim fails.","tokens_in":14308,"feed_emoji":"⚡","tokens_out":915,"duration_ms":7855,"temperature":0.7,"pith_summary":"This paper proposes that an inversion-asymmetric ferroelectric Josephson junction can act as a magnetic-field-free superconducting diode, but only as a history-dependent effect. When bias current is swept hard enough to reverse the ferroelectric polarization, the two polarization states set different critical currents, so the junction switches to the resistive state at unequal thresholds for positive and negative current. The diode efficiency equals the polarization-induced asymmetry factor and vanishes if the polarization never switches. Using a coupled dynamical model that joins a polarization-dependent RCSJ equation to Landau–Khalatnikov–Tani ferroelectric dynamics, the authors show the asymmetry is tunable by ferroelectric parameters and the sweep protocol, appears in both critical and retrapping currents, and survives thermal noise. The result points to electrically programmable, field-free nonreciprocal superconducting elements based on modest-polarization ferroelectrics.","feed_headline":"Polarization flip turns a Josephson junction into a diode","feed_subtitle":"No magnetic field needed: history-dependent critical currents arise when ferroelectric polarization switches under bias","key_machinery":"Coupled phase–polarization dynamics: a polarization-dependent RCSJ equation I = C_0 V̇ + (1 − θP)V/R_0 + (1 − θP)I_c sin ϕ together with Landau–Khalatnikov–Tani ferroelectric dynamics. Polarization switching in the resistive state rewrites the critical-current magnitude for the reverse sweep.","core_discovery":"In an inversion-asymmetric ferroelectric Josephson junction, current-induced polarization switching during a bias sweep produces unequal critical currents |i_c^+| = 1 + θ̃ and |i_c^-| = 1 − θ̃ (and likewise asymmetric retrapping currents). The resulting nonreciprocity is a pseudo-superconducting-diode effect: it is history-dependent, equals the asymmetry factor θ̃, and disappears when polarization does not switch.","pith_inferences":["Because the diode is purely history-dependent, a single preparatory polarization-writing pulse could program the preferred current direction without continuous magnetic bias.","The same coupled dynamics should produce measurable transient voltage spikes or drops during the polarization flip, offering a real-time electrical signature of the switching event.","If resonance between Josephson and ferroelectric modes can be engineered, the diode efficiency or retrapping currents may show additional voltage-step features usable for sensing or multi-state memory."],"forward_implications":["Diode efficiency is electrically set by junction design and spontaneous polarization and equals the asymmetry factor θP0.","Materials with modest polarization and ultrathin barriers are preferred because they allow voltage-driven switching under realistic bias.","The effect remains usable at finite temperature; thermal noise broadens distributions but does not erase the directional asymmetry.","Sweep protocol itself becomes a control knob: below the switching threshold the diode vanishes; above it the device is nonreciprocal.","FE-JJs become candidates for magnetic-field-free, electrically programmable nonreciprocal superconducting circuit elements."],"fun_headline_variants":["Ferroelectric flip makes Josephson junction a field-free diode","Polarization switch yields asymmetric critical supercurrents","History-dependent diode effect in ferroelectric Josephson junctions","Current-driven polarization creates pseudo-superconducting diode","Bias sweep turns inversion-asymmetric JJ into supercurrent rectifier"],"cache_read_input_tokens":128,"weakest_assumption_plain":"The critical current and resistance stay linearly proportional to polarization at the modest spontaneous polarization needed for voltage-driven switching; a larger polarization would deepen the double well and block the switch that creates the diode effect.","fun_headline_variants_meta":{"raw":{"variants":["Ferroelectric flip makes Josephson junction a field-free diode","Polarization switch yields asymmetric critical supercurrents","History-dependent diode effect in ferroelectric Josephson junctions","Current-driven polarization creates pseudo-superconducting diode","Bias sweep turns inversion-asymmetric JJ into supercurrent rectifier"]},"model":"grok-4.5","effort":"low","cost_usd":0.005222,"raw_usage":{"total_tokens":1355,"prompt_tokens":679,"num_sources_used":0,"completion_tokens":63,"cost_in_usd_ticks":52220000,"prompt_tokens_details":{"text_tokens":679,"audio_tokens":0,"image_tokens":0,"cached_tokens":128},"completion_tokens_details":{"audio_tokens":0,"reasoning_tokens":613,"accepted_prediction_tokens":0,"rejected_prediction_tokens":0}},"tokens_in":679,"tokens_out":63,"duration_ms":6482,"temperature":1.0,"reasoning_tokens":613,"cache_read_input_tokens":128,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-07-11T19:27:09.108750+00:00","model_set":{"reader":"grok-4.5"},"falsifier":"Fabricate an inversion-asymmetric FE-JJ with small spontaneous polarization (e.g., CuInP2S6-like), sweep bias past the polarization-switching threshold, and check whether the measured critical currents reverse with polarization history and give diode efficiency equal to the designed asymmetry factor; if polarization never switches or the critical currents remain equal, the claim fails.","supporting_citations":[],"review_version":1}