arxiv: 2605.00577 · v1 · submitted 2026-05-01 · ❄️ cond-mat.supr-con

Recognition: unknown

Long range proximity effects in planar structures involving the halfmetal ferromagnet La0.7Sr0.3MnO3 and Pt interlayers

Jan Aarts, Julian van Doorn, Junxiang Yao, Mariona Cabero

Pith reviewed 2026-05-09 18:35 UTC · model grok-4.3

classification ❄️ cond-mat.supr-con

keywords proximity effecttriplet supercurrenthalf-metallic ferromagnetJosephson junctionLSMOPt interlayerplanar structures

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The pith

Pt interlayers enable zero-resistance states at 2 micrometer distances in LSMO-based planar Josephson junctions

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

The paper extends earlier studies of triplet supercurrent transport in planar nanostrip Josephson junctions that use the half-metallic ferromagnet La0.7Sr0.3MnO3 (LSMO) as the weak link between NbTi superconducting electrodes. It examines the dependence of critical current on nanostrip length and width, finding strong supercurrents but no clear scaling laws because fabrication parameters remain hard to control. The central new experiment inserts a Pt layer between LSMO and NbTi by etching electrode structures onto a continuous LSMO film. This yields sharp superconducting transitions and zero-resistance states at an electrode separation of 2 micrometers, together with indications that still larger separations remain possible. The work matters because half-metals can in principle carry fully spin-polarized triplet supercurrents over long distances, which would be valuable for superconducting spintronic devices if the range can be made reliable.

Core claim

When a Pt interlayer is placed between the LSMO film and the NbTi electrodes, the resulting planar junctions display sharp superconducting transitions and reach a zero-resistance state at an electrode distance of 2 micrometers, with evidence that even larger distances should be accessible.

What carries the argument

The Pt interlayer at the LSMO/NbTi interface, which promotes conversion to triplet correlations that propagate through the half-metallic LSMO over micrometer-scale distances.

If this is right

Triplet supercurrents can be sustained across LSMO lengths of at least 2 micrometers when a Pt interlayer is used.
The absence of simple length or width scaling in the nanostrip devices points to insufficient control over interface or material parameters during fabrication.
The trend observed with Pt interlayers suggests that electrode separations substantially larger than 2 micrometers remain experimentally reachable.
The Pt layer improves interface transparency or spin-mixing compared with direct NbTi-LSMO contacts.

Where Pith is reading between the lines

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

If the supercurrent is confirmed to be triplet and fully spin-polarized, the platform could be used to test superconducting spin valves or long-range spin transport in hybrid devices.
Systematic variation of Pt thickness or substitution of other interlayers would help isolate which interface property controls the triplet generation efficiency.
Mapping the temperature and magnetic-field dependence of the critical current across many devices would provide a quantitative test of the proximity-effect decay length inside the LSMO.

Load-bearing premise

The measured zero-resistance states arise from triplet supercurrent flowing through the LSMO rather than from fabrication shorts, unintended interface paths, or other artifacts.

What would settle it

Fabricating and measuring control devices in which the LSMO layer is absent or replaced by a normal metal while keeping the Pt/NbTi electrode geometry identical, and checking whether the zero-resistance state at 2 micrometers disappears.

Figures

Figures reproduced from arXiv: 2605.00577 by Jan Aarts, Julian van Doorn, Junxiang Yao, Mariona Cabero.

**Figure 1.** Figure 1: Layout and SEM image of the LJ (upper row) and FF (lower row) devices. (a) NbTi top view at source ↗

**Figure 2.** Figure 2: Transport properties of the LJ devices. (a) Resistance view at source ↗

**Figure 3.** Figure 3: Resistance R versus temperature T for the three full film devices (a) FF7, (b) FF9 and (c) FF11, discussed in the text. In (a) two traces are shown, one for increasing temperature (orange circles), and one for decreasing temperature (blue triangles). In (c) the change in R(T) after another 2 minute Ar-etch step is also shown. The measurements were performed with an applied current of 1 µA. (HAADF image) of… view at source ↗

**Figure 4.** Figure 4: Superconducting Quantum Interference (SQI) patterns, represented as a color plot of voltage view at source ↗

**Figure 5.** Figure 5: AFM images of the surface of (a) an LSMO/Ag bilayer and (b) an LSMO/Pt bilayer. In the view at source ↗

**Figure 6.** Figure 6: STEM EELS characterization of an LSMO/Pt/NbTi sample grown on an LSAT substrate. view at source ↗

read the original abstract

Over the last decade, there has been steady research on superconducting junctions with a ferromagnet as the weak link, and where triplet correlations can transport supercurrents over a substantial distances. Of particular interest are halfmetallic ferromagnets, in which only one spin band is present, so that, presumably, the induced supercurrent is fully spin-polarized. We have earlier reported on a study of triplet transport in planar La0.7Sr0.3MnO3(LSMO) nanostrip Josephson junctions with NbTi superconducting contacts, where we found high values for the supercurrents, and large junction lengths (up to 1.3 {\mu}m). Here, we extend that work by studying the dependence of the critical current Ic on the length of the nanostrip between the contacts and the width of the strip. All junctions show strong supercurrents, but we do not observe simple systematics. Apparently, the fabrication process does not allow sufficient control over some of its parameters. To gain more insight in the mechanism for triplet generation at the LSMO/NbTi interface, we also studied the effect of Pt as an interlayer between the LSMO and the NbTi. For this, we etched a NbTi/Pt electrode structure on a full film of LSMO. The results are highly promising, showing sharp superconducting transitions and zero-resistance states being reached at an electrode distance of 2 {\mu}m, with indications that larger distances should be feasible.

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

Pt interlayers push zero-resistance to 2 μm in these LSMO nanostrips, but missing controls leave the triplet mechanism unproven.

read the letter

The new piece here is the Pt interlayer data: they etch NbTi/Pt electrodes onto a full LSMO film and report sharp transitions plus zero resistance at 2 μm spacing, with hints that longer distances might work. That extends their earlier direct LSMO/NbTi junctions (up to 1.3 μm) and gives a concrete experimental configuration to test interface effects on triplet generation. They also checked length and width dependence on the nanostrips, which is a reasonable next step even if the results lack simple systematics. The fabrication note that parameters are hard to control is honest and matches what the stress-test flags. The main soft spot is the absence of anything that rules out shorts, pinholes, or stray Pt/LSMO paths carrying the current instead of triplet supercurrent through the LSMO. No resistance maps, cross-section images, or control devices without the LSMO channel are mentioned, so the zero-resistance claim at 2 μm stays ambiguous. The abstract is thin on quantitative Ic data, error bars, or statistics, which makes it difficult to judge how robust the effect really is. This is for people already working on half-metal Josephson junctions and spin-polarized supercurrents; they will see the Pt trick as a useful variation worth trying, but anyone outside that niche will find the evidence too preliminary to act on. The work shows clear experimental thinking and cites the relevant prior literature without circularity. It deserves a serious referee because the topic matters for low-dissipation spintronics and the Pt results are new enough to warrant scrutiny, even if the paper needs added controls and raw data before publication.

Referee Report

2 major / 1 minor

Summary. The manuscript extends prior work on triplet supercurrent in planar LSMO nanostrip Josephson junctions with NbTi contacts by examining Ic dependence on nanostrip length and width, noting absence of simple systematics due to fabrication variability. It further investigates Pt interlayers between LSMO and NbTi, reporting sharp superconducting transitions and zero-resistance states at 2 μm electrode spacing, with indications that larger distances may be feasible via long-range triplet proximity effects in the half-metal.

Significance. If the zero-resistance states are unambiguously due to spin-polarized triplet supercurrents through LSMO (rather than artifacts), the results would meaningfully extend the demonstrated range of triplet proximity in half-metals beyond the prior 1.3 μm and highlight Pt as an effective interlayer for interface engineering. This would be of interest for superconducting spintronics, though the acknowledged fabrication limitations and lack of quantitative controls temper the immediate impact.

major comments (2)

[Abstract and experimental results on Pt interlayers] Abstract and Pt interlayer results: The central claim that zero-resistance at 2 μm electrode distance arises from triplet supercurrent propagating through the LSMO channel requires explicit exclusion of fabrication artifacts. The text notes that 'the fabrication process does not allow sufficient control over some of its parameters' but provides no description of control devices (e.g., without LSMO channel), cross-sectional imaging, or resistance mapping to rule out micro-shorts, pinholes, or unintended Pt/LSMO paths. This is load-bearing for attributing the effect to the intended mechanism.
[Abstract] Abstract: The report of 'strong supercurrents' and 'zero-resistance states being reached at an electrode distance of 2 μm' lacks accompanying quantitative Ic vs. length data, error bars, number of devices measured, or statistical analysis. Without these, the claim that 'larger distances should be feasible' remains qualitative and cannot be rigorously evaluated against the skeptic concern of unintended conduction paths.

minor comments (1)

[Abstract] The abstract would be strengthened by specifying the number of junctions tested and typical Ic values or transition widths to provide context for the 'highly promising' results.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for the careful reading and constructive comments on our manuscript. We address each major point below and indicate where revisions will be made to strengthen the presentation of the Pt interlayer results and the abstract claims.

read point-by-point responses

Referee: Abstract and experimental results on Pt interlayers: The central claim that zero-resistance at 2 μm electrode distance arises from triplet supercurrent propagating through the LSMO channel requires explicit exclusion of fabrication artifacts. The text notes that 'the fabrication process does not allow sufficient control over some of its parameters' but provides no description of control devices (e.g., without LSMO channel), cross-sectional imaging, or resistance mapping to rule out micro-shorts, pinholes, or unintended Pt/LSMO paths. This is load-bearing for attributing the effect to the intended mechanism.

Authors: We agree that explicit exclusion of fabrication artifacts is important for confidently attributing the zero-resistance states to triplet supercurrents through the LSMO. The manuscript acknowledges fabrication variability but does not describe control devices or imaging. In the revised version we will add a paragraph discussing potential artifacts, noting that the sharp superconducting transitions and the extension beyond our prior 1.3 μm results are inconsistent with random micro-shorts or pinholes, which would not produce such consistent behavior. We will also reference additional SEM images of the electrode structures already obtained during fabrication to confirm the intended geometry and separation. Comprehensive resistance mapping of every device was not performed, but the reproducibility across the measured devices supports the channel-mediated mechanism. revision: partial
Referee: Abstract: The report of 'strong supercurrents' and 'zero-resistance states being reached at an electrode distance of 2 μm' lacks accompanying quantitative Ic vs. length data, error bars, number of devices measured, or statistical analysis. Without these, the claim that 'larger distances should be feasible' remains qualitative and cannot be rigorously evaluated against the skeptic concern of unintended conduction paths.

Authors: We agree that the abstract would benefit from greater quantitative detail to support the claims and allow rigorous evaluation. The main text already presents Ic data versus nanostrip length and width, although without simple systematics owing to fabrication variability. In the revised manuscript we will update the abstract to include specific quantitative information drawn from the reported measurements, such as the range of observed critical currents at 2 μm spacing and the number of devices exhibiting zero-resistance states. This will make the statement that larger distances should be feasible more concrete while still acknowledging the variability. revision: yes

Circularity Check

0 steps flagged

Purely experimental report with no derivations or fitted predictions

full rationale

This manuscript is a purely experimental study reporting measurements of supercurrents, critical currents, superconducting transitions, and zero-resistance states in LSMO nanostrip junctions with and without Pt interlayers. No equations, derivations, ansatzes, or parameter fittings appear in the text; all claims rest on direct fabrication and transport data. Self-citations to prior work by the authors are present but are not load-bearing for any derivation chain, as no such chain exists. The results are therefore self-contained against external benchmarks with no possibility of circular reduction.

Axiom & Free-Parameter Ledger

0 free parameters · 1 axioms · 0 invented entities

Experimental paper; central observations rest on standard assumptions of the superconducting spintronics field rather than new free parameters or invented entities.

axioms (1)

domain assumption Triplet superconducting correlations can be generated at superconductor/half-metal interfaces and propagate over long distances.
Invoked implicitly when interpreting the observed supercurrents as triplet transport.

pith-pipeline@v0.9.0 · 5590 in / 1185 out tokens · 36783 ms · 2026-05-09T18:35:23.928720+00:00 · methodology

discussion (0)

Reference graph

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