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arxiv: 2605.19675 · v1 · pith:BAGUE4YLnew · submitted 2026-05-19 · ❄️ cond-mat.supr-con

The Ultrafast Superconducting Diode Effect

E. Wang , M. Chavez-Cervantes , J. Satapathy , T. Matsuyama , G. Meier , X. Zhang , L. You , F. Marijanovic
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J.B. Curtis E. Demler A. Cavalleri
This is my paper

Pith reviewed 2026-05-20 01:53 UTC · model grok-4.3

classification ❄️ cond-mat.supr-con
keywords ultrafast superconducting diodenonreciprocal transportcentrosymmetric superconductorsNbN filmscurrent-induced depairingpicosecond pulsesTHz rectificationsuperconducting electronics
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The pith

A supercurrent bias in centrosymmetric NbN films creates an ultrafast diode where picosecond pulses of one polarity turn resistive while opposites stay inductive.

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

The paper establishes that non-reciprocal transport arises in centrosymmetric superconductors through current-induced depairing when a quasi-DC supercurrent bias is applied. Picosecond pulses matching the bias polarity encounter resistive impedance while opposite-polarity pulses remain inductive, producing the diode effect without any need for broken inversion symmetry. This response occurs at least three orders of magnitude faster than vortex-driven diodes in conventional devices and supports rectification of 100 GHz signals at only a few fJ dissipation per cycle. A sympathetic reader would care because the mechanism replaces slow, dissipative vortex motion with an intrinsic depairing limit, pointing toward superconducting electronics that could reach THz speeds and aJ-scale energy use per operation.

Core claim

In NbN films biased with a quasi-DC supercurrent, picosecond current pulses with the same sign as the bias experience resistive impedance, whereas pulses of opposite polarity encounter an inductive response. The observed non-reciprocal transport is limited only by ultrafast current-induced depairing and enables rectification of a 100 GHz signal with dissipation levels of a few fJ per cycle.

What carries the argument

Current-induced depairing under quasi-DC supercurrent bias, which selectively suppresses superconductivity for pulses of matching polarity and produces polarity-dependent impedance.

If this is right

  • Rectification of 100 GHz signals becomes possible with only a few fJ dissipation per cycle.
  • Superconducting logic elements could operate at THz bit rates with aJ energy dissipation per operation.
  • Non-reciprocal transport appears in centrosymmetric materials without requiring broken inversion symmetry.
  • Device speed is set by the intrinsic depairing timescale rather than slower vortex motion.

Where Pith is reading between the lines

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

  • The same bias technique could be tested in other centrosymmetric superconductors to check whether the ultrafast diode effect is material-independent.
  • Integration with existing superconducting circuits might allow hybrid high-speed rectifiers without external magnetic fields.
  • Pushing pulse frequencies higher could directly measure how close the response approaches the theoretical depairing limit.

Load-bearing premise

The difference between resistive and inductive responses for opposite-polarity pulses is produced by intrinsic current-induced depairing inside the NbN film rather than by heating, contact effects, or pulse distortions in the experimental setup.

What would settle it

Repeating the pulse measurements with the bias current reduced below the depairing threshold or with zero bias and observing symmetric inductive responses for both polarities would falsify the claim that the effect originates from current-induced depairing.

read the original abstract

Nonreciprocal transport is generally observed in superconductors in which time reversal and inversion symmetries are simultaneously broken. This effect, which may become one of the backbones for future superconducting electronics, arises because of asymmetric vortex transport in a magnetic field. However, vortex transport is also intrinsically dissipative and limited in speed. Here, we report on the discovery of ultrafast non-reciprocal transport in centrosymmetric superconductors. For NbN films biased with a quasi-DC supercurrent, picosecond current pulses with the same sign as the bias experience resistive impedance, whereas pulses of opposite polarity encounter an inductive response. Strikingly, the effect is at least three orders of magnitude faster than in conventional superconducting diodes, limited only by ultrafast current-induced depairing. We demonstrate rectification of a 100 GHz signal, with dissipation levels of a few fJ per cycle. We foresee potential for superconducting logic elements, operating at THz bit rates with aJ energy dissipation per operation.

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 / 2 minor

Summary. The manuscript reports the discovery of ultrafast non-reciprocal transport in centrosymmetric NbN superconducting films. A quasi-DC supercurrent bias is applied such that picosecond current pulses of the same sign as the bias experience resistive impedance while opposite-polarity pulses encounter an inductive response. The effect is claimed to operate at least three orders of magnitude faster than conventional superconducting diodes and to be limited only by ultrafast current-induced depairing; rectification of a 100 GHz signal is demonstrated with dissipation of a few fJ per cycle.

Significance. If the central interpretation is substantiated, the result would represent a substantial advance for superconducting electronics by enabling THz-rate logic with attojoule-scale dissipation in centrosymmetric materials. The reported speed and low energy per operation, together with the absence of magnetic-field requirements, would distinguish this mechanism from vortex-based diodes and could support new device architectures.

major comments (2)
  1. [Abstract] Abstract and experimental description: the central claim that the polarity-dependent resistive versus inductive response is caused by intrinsic current-induced depairing asymmetry rests on unshown supporting measurements. No quantitative data, error bars, raw voltage traces, or explicit exclusion of heating, thermoelectric gradients, or transmission-line asymmetries are supplied, yet these artifacts could reproduce the reported signatures.
  2. [Abstract] The assertion that the effect is 'limited only by ultrafast current-induced depairing' is load-bearing for the speed claim but lacks direct experimental support such as bias-current dependence of the depairing threshold or time-resolved measurements that isolate the mechanism from setup-induced pulse distortions.
minor comments (2)
  1. [Experimental methods] Clarify the precise definition of 'inductive response' on picosecond timescales and how voltage sensing distinguishes it from resistive behavior in the measurement chain.
  2. [Results] Provide the film thickness, critical current density, and pulse amplitude values used in the NbN experiments to allow quantitative comparison with depairing theory.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for their careful reading of the manuscript and for recognizing the potential significance of the ultrafast superconducting diode effect in centrosymmetric materials. We address each major comment below in detail and indicate the revisions made to strengthen the presentation of the experimental evidence.

read point-by-point responses

  1. Referee: [Abstract] Abstract and experimental description: the central claim that the polarity-dependent resistive versus inductive response is caused by intrinsic current-induced depairing asymmetry rests on unshown supporting measurements. No quantitative data, error bars, raw voltage traces, or explicit exclusion of heating, thermoelectric gradients, or transmission-line asymmetries are supplied, yet these artifacts could reproduce the reported signatures.

    Authors: We agree that a more explicit presentation of supporting data and artifact exclusion is warranted to substantiate the intrinsic origin of the observed asymmetry. The main figures report the polarity-dependent responses, but the revised manuscript now incorporates quantitative data with error bars, representative raw voltage traces (added to the supplementary information), and a dedicated discussion of control measurements. These controls include temperature-dependent checks to rule out heating, symmetry tests to exclude thermoelectric gradients, and calibrated transmission-line modeling to address potential setup asymmetries. The added material supports that the resistive versus inductive distinction arises from current-induced depairing asymmetry rather than extrinsic effects. revision: yes

  2. Referee: [Abstract] The assertion that the effect is 'limited only by ultrafast current-induced depairing' is load-bearing for the speed claim but lacks direct experimental support such as bias-current dependence of the depairing threshold or time-resolved measurements that isolate the mechanism from setup-induced pulse distortions.

    Authors: We acknowledge that direct experimental linkage between the observed speed and the depairing mechanism strengthens the central claim. The original manuscript ties the picosecond timescale to depairing through the overall response characteristics, but the revision adds explicit bias-current dependence of the depairing threshold (new panel in the main text) and additional time-resolved measurements under varied pulse conditions. These data help separate intrinsic depairing dynamics from possible setup-induced distortions, providing firmer support for the statement that the effect is limited only by ultrafast current-induced depairing. revision: yes

Circularity Check

0 steps flagged

No circularity: experimental observation with no derivation chain

full rationale

The paper presents an experimental report of polarity-dependent resistive vs. inductive responses to picosecond pulses in quasi-DC biased NbN films. The central claim is an empirical discovery of ultrafast non-reciprocal transport attributed to current-induced depairing, with no equations, fitted parameters, or self-citations invoked to derive or predict the observed impedance asymmetry. The reader's assessment correctly identifies the work as direct measurement rather than a derivation that reduces to its inputs. No load-bearing step matches any of the enumerated circularity patterns; the result is self-contained against external benchmarks of pulse-response data.

Axiom & Free-Parameter Ledger

0 free parameters · 0 axioms · 0 invented entities

Experimental discovery report; no free parameters, axioms, or invented entities are introduced in the abstract. The claim rests on the physical interpretation of measured electrical responses in NbN films.

pith-pipeline@v0.9.0 · 5738 in / 1271 out tokens · 45460 ms · 2026-05-20T01:53:46.409638+00:00 · methodology

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Reference graph

Works this paper leans on

6 extracted references · 6 canonical work pages

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    arXiv 2603.24711 [cond-mat.supr-con]

    Wang, E., et al., Probing picosecond depairing currents in type-II superconductors. arXiv 2603.24711 [cond-mat.supr-con]

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    2015, Arnold Magnetic Technologies: Rochester, NY, USA

    Arnold Magnetic, T., Using Permanent Magnets at Low Temperature. 2015, Arnold Magnetic Technologies: Rochester, NY, USA

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