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arxiv: 2509.14109 · v2 · submitted 2025-09-17 · ❄️ cond-mat.mes-hall · cond-mat.supr-con

Giant field-free transverse Josephson diode effect in altermagnets

Pith reviewed 2026-05-18 15:59 UTC · model grok-4.3

classification ❄️ cond-mat.mes-hall cond-mat.supr-con
keywords altermagnetsJosephson diode effecttransverse supercurrentRashba spin-orbit couplingnonreciprocal transportNéel vectorfour-terminal junction
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The pith

Altermagnets with Rashba spin-orbit coupling produce a field-free transverse Josephson diode effect with efficiencies above 3000 percent in four-terminal junctions.

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

The paper shows that altermagnets combined with Rashba spin-orbit coupling in a four-terminal Josephson junction geometry generate nonreciprocal transverse supercurrents without any external magnetic field. A longitudinal phase bias drives these currents to flow preferentially in one direction, producing a strong diode-like response along with an anomalous phase shift. Both the transverse and longitudinal effects can be adjusted by rotating the internal Néel vector and persist even with moderate disorder or imperfect interfaces. A reader would care because this setup offers a way to control superconducting current direction using only the material's built-in order rather than applied fields.

Core claim

The authors predict that altermagnets with Rashba spin-orbit coupling in four-terminal Josephson junctions support a transverse Josephson diode effect that remains field-free, where a longitudinal phase bias generates nonreciprocal transverse supercurrents and a finite anomalous phase shift, while the longitudinal current itself shows a Josephson diode effect, with both responses tunable via the Néel vector orientation and diode efficiencies exceeding 3000 percent, and the effect robust against moderate disorder and imperfect interfaces.

What carries the argument

The four-terminal Josephson junction geometry that combines altermagnetic order with Rashba spin-orbit coupling, allowing nonreciprocal transverse supercurrents to emerge directly from the microscopic Hamiltonian and to be controlled by the Néel vector.

If this is right

  • Unidirectional transverse supercurrents appear without external magnetic fields.
  • Diode efficiencies reach values exceeding 3000 percent.
  • Both transverse and longitudinal responses remain tunable by the Néel vector orientation.
  • The nonreciprocity persists under moderate disorder and imperfect interfaces.

Where Pith is reading between the lines

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

  • The combination could support field-free nonreciprocal elements in superconducting circuits for low-dissipation electronics.
  • Similar transverse nonreciprocity may occur in other antiferromagnetic systems that also carry strong spin-orbit effects.
  • Measuring the asymmetry in transverse current as a function of Néel vector angle in fabricated devices would directly test the prediction.

Load-bearing premise

Rashba spin-orbit coupling can be combined with altermagnetic order in the four-terminal Josephson geometry such that the transverse supercurrent nonreciprocity emerges robustly from the microscopic Hamiltonian without requiring fine-tuned parameters or external fields.

What would settle it

Fabricating a four-terminal Josephson junction on an altermagnet with Rashba spin-orbit coupling and measuring whether the transverse current-voltage curve shows nonreciprocity with efficiency above 3000 percent in the complete absence of magnetic fields.

Figures

Figures reproduced from arXiv: 2509.14109 by Abhiram Soori, Bijay Kumar Sahoo.

Figure 1
Figure 1. Figure 1: FIG. 1. Schematic of the proposed four-terminal junction. [PITH_FULL_IMAGE:figures/full_fig_p002_1.png] view at source ↗
Figure 2
Figure 2. Figure 2: FIG. 2. CPR: Transverse Josephson current ( [PITH_FULL_IMAGE:figures/full_fig_p002_2.png] view at source ↗
Figure 5
Figure 5. Figure 5: FIG. 5. (a) Transverse critical currents ( [PITH_FULL_IMAGE:figures/full_fig_p003_5.png] view at source ↗
Figure 3
Figure 3. Figure 3: FIG. 3. Transverse (Longitudinal) diode effect coefficient [PITH_FULL_IMAGE:figures/full_fig_p003_3.png] view at source ↗
Figure 6
Figure 6. Figure 6: FIG. 6. CPR: transverse Josephson current ( [PITH_FULL_IMAGE:figures/full_fig_p003_6.png] view at source ↗
Figure 4
Figure 4. Figure 4: FIG. 4. (a) Transverse (Longitudinal) diode effect coefficient [PITH_FULL_IMAGE:figures/full_fig_p003_4.png] view at source ↗
Figure 7
Figure 7. Figure 7: FIG. 7. Transverse (Longitudinal) diode effect coefficient [PITH_FULL_IMAGE:figures/full_fig_p004_7.png] view at source ↗
Figure 8
Figure 8. Figure 8: FIG. 8. (a) Transverse (Longitudinal) diode effect coefficient [PITH_FULL_IMAGE:figures/full_fig_p004_8.png] view at source ↗
Figure 9
Figure 9. Figure 9: FIG. 9. (a) Transverse diode effect coefficient [PITH_FULL_IMAGE:figures/full_fig_p004_9.png] view at source ↗
Figure 10
Figure 10. Figure 10: FIG. 10. Energy versus superconducting phase difference [PITH_FULL_IMAGE:figures/full_fig_p009_10.png] view at source ↗
read the original abstract

We predict a field-free transverse Josephson diode effect in altermagnets (AMs) with Rashba spin--orbit coupling, achieving diode efficiencies exceeding $3000\%$ and unidirectional transverse supercurrents in four-terminal junctions. In this geometry, a longitudinal phase bias generates transverse supercurrents that exhibit nonreciprocity and a finite anomalous phase shift, while the longitudinal current itself displays a Josephson diode effect. Both responses are tunable via the N\'eel vector orientation. We further show that the effect remains robust against moderate disorder and imperfect interfaces. These results establish AMs as a promising platform for nonreciprocal superconducting transport, with clear routes toward experimental realization.

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

0 major / 3 minor

Summary. The manuscript presents a theoretical study of four-terminal Josephson junctions incorporating altermagnets with Rashba spin-orbit coupling. It predicts a field-free transverse Josephson diode effect featuring diode efficiencies exceeding 3000%, unidirectional transverse supercurrents, nonreciprocity accompanied by an anomalous phase shift, a conventional Josephson diode effect in the longitudinal channel, and tunability by Néel-vector orientation. The predictions are obtained from a microscopic Hamiltonian and are reported to remain robust under moderate disorder and imperfect interfaces.

Significance. If the central predictions hold, the work identifies altermagnets as a promising platform for field-free nonreciprocal superconducting transport with exceptionally high efficiencies. The explicit microscopic derivation, demonstration of Néel-vector tunability, and numerical checks of robustness to disorder constitute clear strengths that could guide experimental efforts in mesoscopic superconductivity and spintronics.

minor comments (3)
  1. [Results section] The precise definition of diode efficiency (e.g., the ratio of critical currents or the normalized form used to obtain values >3000%) should be stated explicitly in the main text or methods, together with the corresponding equation.
  2. [Figure 2 and Figure 3] Figure captions for the current-phase relations and efficiency plots would benefit from indicating the specific values of the Rashba strength, altermagnetic exchange, and junction lengths employed in the calculations.
  3. [Introduction] A brief comparison with existing literature on altermagnetic Josephson junctions or Rashba-based diodes would help situate the reported efficiencies and the transverse geometry.

Simulated Author's Rebuttal

0 responses · 0 unresolved

We thank the referee for their positive and constructive report, which accurately summarizes our main results on the field-free transverse Josephson diode effect in altermagnets. We appreciate the recommendation for minor revision and the recognition of the microscopic derivation, Néel-vector tunability, and robustness checks as strengths. No specific major comments were raised in the report, so we outline our planned minor revisions below and confirm that all points can be addressed.

Circularity Check

0 steps flagged

No significant circularity; derivation self-contained from Hamiltonian

full rationale

The paper constructs a microscopic Bogoliubov-de Gennes Hamiltonian for a four-terminal Josephson junction incorporating altermagnetic exchange and Rashba SOC, then computes the transverse supercurrent and diode efficiency by direct numerical solution of the scattering problem or BdG equations. No parameters are fitted to the target observables; the reported >3000% efficiencies and field-free nonreciprocity follow from the model equations without self-definition or renaming of known results. Self-citations, if present, are not load-bearing for the central prediction. The derivation is therefore independent and falsifiable against external benchmarks.

Axiom & Free-Parameter Ledger

0 free parameters · 1 axioms · 0 invented entities

Based on abstract only; the prediction rests on standard Bogoliubov-de Gennes modeling of Josephson junctions plus altermagnetic and Rashba terms whose explicit forms are not shown.

axioms (1)
  • domain assumption Standard mean-field treatment of superconductivity in the presence of altermagnetic order and Rashba spin-orbit coupling
    Invoked implicitly to obtain the supercurrent-phase relations

pith-pipeline@v0.9.0 · 5644 in / 1296 out tokens · 32194 ms · 2026-05-18T15:59:49.286553+00:00 · methodology

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Forward citations

Cited by 1 Pith paper

Reviewed papers in the Pith corpus that reference this work. Sorted by Pith novelty score.

  1. Geometry induced net spin polarization of $d$-wave altermagnets

    cond-mat.mes-hall 2025-12 unverdicted novelty 7.0

    Rectangular d-wave altermagnets acquire net spin polarization from geometry-induced imbalance in occupied spin states via anisotropic Fermi contours and finite-size k-space sampling, vanishing when Lx equals Ly or in ...

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