Supercurrent spin Hall effect enabled nanopillar Josephson diodes

Debashree Nayak; Dimple Rani; Kartik Senapati; Prasanjit Samal

arxiv: 2605.17066 · v1 · pith:Z75OXGIXnew · submitted 2026-05-16 · ❄️ cond-mat.supr-con

Supercurrent spin Hall effect enabled nanopillar Josephson diodes

Debashree Nayak , Dimple Rani , Prasanjit Samal , Kartik Senapati This is my paper

Pith reviewed 2026-05-20 15:00 UTC · model grok-4.3

classification ❄️ cond-mat.supr-con

keywords Josephson diodesupercurrent spin-Hall effectnanopillar Josephson junctionnonreciprocal supercurrentspin segregationNb-Pt-Nb junctionfield tunable diodesuperconducting diode

0 comments

The pith

Nanopillar Josephson junctions with platinum barriers achieve 17% diode efficiency above liquid helium temperature using the supercurrent spin-Hall effect.

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

This paper shows how non-reciprocity can be created in Josephson junctions by using the supercurrent spin-Hall effect inside a platinum barrier layer. In a series of Nb-Pt-Nb nanopillar devices, the bias current itself produces a net spin segregation in the barrier. An external magnetic field then shifts the junction phase in opposite ways for current flowing in each direction, producing diode-like behavior that reaches 17% efficiency at temperatures above 4 K. A reader would care because the method uses only the intrinsic properties of a heavy metal barrier and does not require added Rashba spin-orbit layers, opening a route to non-reciprocal superconducting elements that function under less extreme cooling conditions.

Core claim

The authors establish that non-reciprocity in these Josephson junctions arises from the supercurrent spin-Hall effect in the Pt barrier, which produces a net non-equilibrium spin segregation. Since the direction of the induced spin moment is set by the bias current, an external magnetic field causes the associated phases to add with opposite signs for opposite current directions. This results in a nonreciprocal supercurrent, enabling field-tunable Josephson diode efficiencies as high as 17% measured above liquid helium temperature in the Nb-Pt-Nb nanopillar junctions.

What carries the argument

The supercurrent spin-Hall effect in the heavy-metal barrier that generates bias-current-dependent spin segregation, which couples to an external field to create opposite phase shifts for forward and reverse supercurrents.

If this is right

Josephson diodes become possible with higher efficiencies at temperatures above liquid helium.
The diode effect is tunable by the external magnetic field strength and direction.
Non-reciprocity can be achieved using intrinsic spin-orbit coupling in the barrier without additional symmetry-breaking layers.
The nanopillar geometry supports the realization of this effect in compact superconducting junctions.

Where Pith is reading between the lines

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

This approach could be tested in other heavy metals to see if larger spin-Hall angles yield even higher diode efficiencies.
Such diodes might be combined with other Josephson junction technologies to create new superconducting circuit elements.
The spin segregation could be probed with additional spin-sensitive experiments to confirm the non-equilibrium dynamics.

Load-bearing premise

The observed non-reciprocity must come from the specific net non-equilibrium spin segregation in the Pt barrier due to the supercurrent spin-Hall effect, where the spin moment direction follows the bias current to make the external field produce opposite phase shifts for opposite currents.

What would settle it

The claim would be falsified by finding no significant diode effect in similar junctions but with a barrier material that has negligible spin-Hall effect, or by measurements showing no correlation between the current direction and the induced spin moment.

Figures

Figures reproduced from arXiv: 2605.17066 by Debashree Nayak, Dimple Rani, Kartik Senapati, Prasanjit Samal.

read the original abstract

In the recent years it has been possible to achieve diode-like, non-reciprocal current-voltage response in Josephson junctions, despite the intrinsic symmetry of the Josephson effect itself. This is typically achieved by incorporating Rashba spin-orbit coupling into the Josephson junction as a strong inversion symmetry breaking component, and external magnetic field as a tuneable time-reversal symmetry breaking component. However, the efficiencies of the external field tuneable Josephson-diodes have remained limited to less than 10 \%, often measured below 100 mK temperature. In this work we take a new approach where non-reciprocity is induced by intrinsic SOC in a heavy metal Josephson barrier via the predicted supercurrent spin-Hall effect. By measuring a series of Nb-Pt-Nb nanopillar junctions we demonstrated field tuneable Josephson diode efficiencies as high as 17\%, measured above liquid Helium temperature. This was possible by the realization of a net non-equilibrium spin segregation in the Pt barrier, due to the supercurrent spin-Hall effect in the Pt barrier, analogous to the normal spin-Hall effect. As the direction of the induced spin moment is determined by the bias current, an external magnetic field causes the associated phases to add with opposite signs for opposite current directions, resulting in a nonreciprocal supercurrent across the junction.

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.

Desk Editor's Note private letter to a colleague

The paper gets 17% field-tunable Josephson diode efficiency in Nb-Pt-Nb nanopillars above 4 K by using supercurrent spin-Hall in the Pt barrier instead of Rashba plus magnet, but the mechanism attribution rests on thin evidence.

read the letter

The main point is that this work demonstrates non-reciprocal supercurrent in Nb-Pt-Nb nanopillar junctions with efficiencies up to 17% at temperatures above liquid helium, using an intrinsic supercurrent spin-Hall effect in the Pt layer to create current-direction-dependent spin segregation that an external field then converts into opposite phase shifts. That replaces the usual Rashba interface plus strong magnet approach and reaches both higher efficiency and higher operating temperature than most prior reports. They measured a series of these junctions and present the field dependence as evidence that the effect is tunable. That part is straightforward and useful if the numbers hold. The paper does a reasonable job framing the concept against existing Josephson diode literature and showing that the heavy-metal barrier can produce the non-reciprocity without added Rashba layers. The practical angle for circuit designers who want to avoid large magnets is clear. The soft spot is the mechanism claim. The abstract ties the observed non-reciprocity specifically to net non-equilibrium spin segregation from the supercurrent spin-Hall effect, but it gives no indication of the controls needed to isolate that from other possibilities such as current crowding in the nanopillar geometry, self-field effects, or fabrication-induced interface asymmetries. Thickness-dependent scaling, lighter-metal control barriers, or symmetric versus asymmetric pillar tests would help, yet none are mentioned. The efficiency figure also appears without error bars or raw I-V curves in the summary, which makes it difficult to judge how robust the 17% value really is. This is the kind of experimental claim that needs the full dataset and those checks before the attribution can be taken as settled. The work is aimed at groups building superconducting sensors, diodes, or logic elements who care about simpler field-tunable non-reciprocity. A reader already working on heavy-metal barriers or spin-Hall effects in superconductors would get the most out of it. I would send it to peer review so referees can ask for the missing controls and data presentation details.

Referee Report

2 major / 1 minor

Summary. The manuscript reports experimental realization of field-tunable Josephson diodes in Nb-Pt-Nb nanopillar junctions. Non-reciprocity is attributed to net non-equilibrium spin segregation in the Pt barrier arising from the supercurrent spin-Hall effect, enabling diode efficiencies up to 17% at temperatures above liquid helium.

Significance. If the central attribution holds and the efficiencies are robustly verified, the result would represent a meaningful step forward for Josephson diodes by demonstrating a route based on intrinsic spin-orbit coupling in a heavy-metal barrier rather than engineered Rashba interfaces, with operation at accessible temperatures.

major comments (2)

Abstract: the reported peak efficiency of 17% is presented without error bars, raw I-V traces, or explicit description of how the value was extracted from the data set; this directly affects verifiability of the headline experimental claim.
Abstract, final paragraph: the load-bearing interpretation that the observed non-reciprocity originates specifically from current-direction-dependent spin accumulation via the supercurrent spin-Hall effect is not secured by controls such as Pt-thickness scaling, lighter-metal barrier references, or symmetric versus asymmetric nanopillar geometries that would exclude current-crowding or interface-asymmetry alternatives.

minor comments (1)

Notation for the efficiency metric and the definition of the external-field direction relative to the nanopillar axis should be made consistent between text and any figures.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for their constructive and detailed review of our manuscript. We address each major comment below and indicate the revisions we will make to improve clarity and strengthen the presentation of our results.

read point-by-point responses

Referee: Abstract: the reported peak efficiency of 17% is presented without error bars, raw I-V traces, or explicit description of how the value was extracted from the data set; this directly affects verifiability of the headline experimental claim.

Authors: We agree that the abstract would benefit from additional details to enhance verifiability. In the revised manuscript, we will update the abstract to include a concise description of how the diode efficiency was extracted from the measured I-V characteristics and will reference the associated uncertainty. The raw I-V traces are shown in the main-text figures, and the full extraction procedure is described in the methods and supplementary information. We will also ensure error bars are explicitly noted for the peak efficiency value. revision: yes
Referee: Abstract, final paragraph: the load-bearing interpretation that the observed non-reciprocity originates specifically from current-direction-dependent spin accumulation via the supercurrent spin-Hall effect is not secured by controls such as Pt-thickness scaling, lighter-metal barrier references, or symmetric versus asymmetric nanopillar geometries that would exclude current-crowding or interface-asymmetry alternatives.

Authors: We acknowledge that dedicated control experiments would further secure the mechanistic attribution. Our existing dataset includes multiple devices with varying Pt thicknesses, and the observed dependence of the diode efficiency on barrier thickness is consistent with the expected behavior for the supercurrent spin-Hall effect. In the revised manuscript we will add an expanded discussion section that explicitly considers alternative mechanisms such as current crowding and interface or geometric asymmetry, and we will explain why the temperature dependence, field tunability, and agreement with theoretical modeling favor the spin-Hall interpretation. While lighter-metal barrier controls and symmetric-geometry comparisons are not included in the present work, we will note these as valuable directions for future studies. revision: partial

Circularity Check

0 steps flagged

No circularity: experimental demonstration relies on direct measurements, not self-referential derivation

full rationale

The paper reports experimental measurements of field-tunable Josephson diode efficiencies (up to 17%) in Nb-Pt-Nb nanopillar junctions above liquid helium temperature. The central claim attributes non-reciprocity to net non-equilibrium spin segregation via the supercurrent spin-Hall effect in the Pt barrier, with the mechanism described as analogous to the normal spin-Hall effect and previously predicted. No equations, fitted parameters, or first-principles derivations are presented that reduce the observed efficiencies or phase shifts to inputs by construction. The efficiency values are measured quantities, not outputs of any internal model or self-citation chain. The interpretation invokes an external predicted effect without load-bearing self-citation or ansatz smuggling that would make the result tautological. This is a standard experimental paper with independent content from the measurements themselves.

Axiom & Free-Parameter Ledger

0 free parameters · 1 axioms · 1 invented entities

The central claim rests on experimental data interpreted through the predicted supercurrent spin-Hall effect; no free parameters are introduced in the abstract, and the interpretation relies on standard superconductivity and spin-orbit physics.

axioms (1)

domain assumption Standard Josephson junction physics and spin-Hall effect in heavy metals hold in the nanopillar geometry.
Invoked when mapping the observed non-reciprocity to spin segregation in the Pt barrier.

invented entities (1)

supercurrent spin-Hall effect no independent evidence
purpose: To generate bias-current-dependent spin segregation that produces non-reciprocal supercurrent when combined with external field.
The effect is described as previously predicted; the paper provides no independent falsifiable test of the effect itself beyond the diode efficiency.

pith-pipeline@v0.9.0 · 5777 in / 1357 out tokens · 39028 ms · 2026-05-20T15:00:11.423568+00:00 · methodology

discussion (0)

Lean theorems connected to this paper

Citations machine-checked in the Pith Canon. Every link opens the source theorem in the public Lean library.

IndisputableMonolith/Cost/FunctionalEquation.lean washburn_uniqueness_aczel unclear

?

unclear
Relation between the paper passage and the cited Recognition theorem.

non-reciprocity is induced by intrinsic SOC in a heavy metal Josephson barrier via the predicted supercurrent spin-Hall effect... net non-equilibrium spin segregation in the Pt barrier
IndisputableMonolith/Foundation/RealityFromDistinction.lean reality_from_one_distinction unclear

?

unclear
Relation between the paper passage and the cited Recognition theorem.

Signature of 0−π transition... oscillatory thickness dependence of T_JJ

What do these tags mean?

matches: The paper's claim is directly supported by a theorem in the formal canon.
supports: The theorem supports part of the paper's argument, but the paper may add assumptions or extra steps.
extends: The paper goes beyond the formal theorem; the theorem is a base layer rather than the whole result.
uses: The paper appears to rely on the theorem as machinery.
contradicts: The paper's claim conflicts with a theorem or certificate in the canon.
unclear: Pith found a possible connection, but the passage is too broad, indirect, or ambiguous to say the theorem truly supports the claim.

Reference graph

Works this paper leans on

15 extracted references · 15 canonical work pages

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Super- conducting diode effect sign change in epitaxial al-inas josephson junctions

Neda Lotfizadeh, William F Schiela, Barı¸ s Pekerten, Peng Yu, Bassel Heiba Elfeky, William M Strickland, Alex Matos-Abiague, and Javad Shabani. Super- conducting diode effect sign change in epitaxial al-inas josephson junctions. Communications Physics, 7(1):120, 2024

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Gate tunable josephson diode effect in joseph- son junctions made from inas nanosheets.Advanced Functional Materials, page 2503401, 2025

Shili Yan, Yi Luo, Haitian Su, Han Gao, Xingjun Wu, Dong Pan, Jianhua Zhao, Ji-Yin Wang, and Hongqi Xu. Gate tunable josephson diode effect in joseph- son junctions made from inas nanosheets.Advanced Functional Materials, page 2503401, 2025

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Gate-tunable josephson diode.Physical Review Applied, 22(5):054034, 2024

Grzegorz P Mazur, Nick van Loo, David van Driel, J-Y Wang, Leo P Kouwen- hoven, G Badawy, S Gazibegovic, and EPAM Bakkers. Gate-tunable josephson diode.Physical Review Applied, 22(5):054034, 2024

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Gate-tunable superconduct- ing diode effect in a three-terminal josephson device.Nature communications, 14(1):3078, 2023

Mohit Gupta, Gino V Graziano, Mihir Pendharkar, Jason T Dong, Connor P Dempsey, Chris Palmstrøm, and Vlad S Pribiag. Gate-tunable superconduct- ing diode effect in a three-terminal josephson device.Nature communications, 14(1):3078, 2023

work page 2023

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Modulation of josephson coupling and superconducting diode effect in twisted nbse 2/nbse 2 van der waals junctions.Physical Review Applied, 25(1):L011003, 2026

Zhi-Hui Ren, Si-Li Wu, Hao-Chen Zhang, Xue-Tao Di, Wen-Yuan Jia, Yi-Xuan Li, Chong Wang, Mao-Yuan Wang, Chuan Li, Cai-Zhen Li, et al. Modulation of josephson coupling and superconducting diode effect in twisted nbse 2/nbse 2 van der waals junctions.Physical Review Applied, 25(1):L011003, 2026

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Josephson diode effect in high-mobility insb nanoflags.Nano Letters, 22(21):8502–8508, 2022

Bianca Turini, Sedighe Salimian, Matteo Carrega, Andrea Iorio, Elia Strambini, Francesco Giazotto, Valentina Zannier, Lucia Sorba, and Stefan Heun. Josephson diode effect in high-mobility insb nanoflags.Nano Letters, 22(21):8502–8508, 2022

work page 2022

[7] [7]

Enhanced superconducting diode effect in hybrid josephson junctions.arXiv preprint arXiv:2512.19017, 2025

Peng Yu, Han Fu, William F Schiela, William Strickland, Bassel Heiba Elfeky, SM Farzaneh, Jacob Issokson, Wei Pan, Enrico Rossi, and Javad Shabani. Enhanced superconducting diode effect in hybrid josephson junctions.arXiv preprint arXiv:2512.19017, 2025

work page arXiv 2025

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Self-field-induced josephson diode effect.Nano Letters, 2025

Arman Rashidi, Sina Ahadi, and Susanne Stemmer. Self-field-induced josephson diode effect.Nano Letters, 2025

work page 2025

[9] [9]

Josephson diode effect in nanowire-based andreev molecules.Communications Physics, 8(1):330, 2025

Shang Zhu, Yiwen Ma, Jiangbo He, Xiaozhou Yang, Zhongmou Jia, Min Wei, Yiping Jiao, Jiezhong He, Enna Zhuo, Xuewei Cao, et al. Josephson diode effect in nanowire-based andreev molecules.Communications Physics, 8(1):330, 2025

work page 2025

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Hohenberg and W

P. Hohenberg and W. Kohn. Inhomogeneous electron gas.Physical Review, 136(3B):B864–B871, 1964. 30

work page 1964

[11] [11]

Kohn and L

W. Kohn and L. J. Sham. Self-consistent equations including exchange and correlation effects.Physical Review, 140(4A):A1133–A1138, 1965

work page 1965

[12] [12]

Weck, Joshua P

Philippe F. Weck, Joshua P. Townsend, Kyle R. Cochrane, Scott D. Crockett, and Nathan W. Moore. Shock compression of niobium from first-principles.Journal of Applied Physics, 125(24):245905, 06 2019

work page 2019

[13] [13]

Sadovskyy, Andrey E

Herv´ e Ness, Ivan A. Sadovskyy, Andrey E. Antipov, Mark van Schilfgaarde, and Roman M. Lutchyn. Supercurrent decay in ballistic magnetic josephson junctions. npj Computational Materials, 8(1):23, 2022

work page 2022

[14] [14]

Magnetic and electronic proper- ties of bulk and clusters of fept l10.Journal of Physics: Condensed Matter, 24(40):406004, sep 2012

Cyrille Barreteau and Daniel Spanjaard. Magnetic and electronic proper- ties of bulk and clusters of fept l10.Journal of Physics: Condensed Matter, 24(40):406004, sep 2012

work page 2012

[15] [15]

S. Baud, C. Ramseyer, G. Bihlmayer, S. Bl¨ ugel, C. Barreteau, M. C. Desjonqu` eres, D. Spanjaard, and N. Bernstein. Comparative study of ab initio and tight-binding electronic structure calculations applied to platinum surfaces.Phys. Rev. B, 70:235423, Dec 2004. 31

work page 2004