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arxiv: 2510.09777 · v2 · submitted 2025-10-10 · ❄️ cond-mat.supr-con · cond-mat.str-el

Emergent Network of Josephson Junctions in a Kagome Superconductor

Tycho J. Blom , Matthijs Rog , Marieke Altena , Andrea Capa Salinas , Stephen D. Wilson , Milan P. Allan , Chuan Li , Kaveh Lahabi This is my paper

Pith reviewed 2026-05-18 08:03 UTC · model grok-4.3

classification ❄️ cond-mat.supr-con cond-mat.str-el
keywords kagome superconductorJosephson junctionscritical current oscillationsCsV3Sb5Shapiro stepsfilamentary supercurrentsuperconducting interferenceAV3Sb5 family
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The pith

Critical current oscillations in CsV3Sb5 flakes arise from an intrinsic network of Josephson junctions that forms below the critical temperature.

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

The paper establishes that critical current oscillations observed in unstructured flakes of the kagome superconductor CsV3Sb5 originate from a network of Josephson junctions that emerges naturally inside the material once cooled below its transition temperature. This matters because it supplies a direct mechanism for supercurrent behavior in materials that combine strong correlations with topological features. Support comes from the appearance of quantized Shapiro steps under radio-frequency radiation, from interference patterns that vary with contact position and match small junctions linked by filamentary paths, and from the survival of main pattern features after the flake is nanostructured and thermally cycled. The results indicate that these junctions are localized and stable.

Core claim

The origin of these oscillations is a network of Josephson junctions intrinsic to the flake that emerges below its critical temperature. Under radio-frequency radiation, quantized Shapiro steps are observed. The sensitivity of the step height to the contact placement indicates a complex network of junctions. By performing interference studies along multiple field directions, the interference effects are shown to result from small junctions and filamentary supercurrent flow. Upon nanostructuring the flake, prominent features of the interference pattern are preserved, illustrating the localized nature of these junctions and their stability to thermal cycles.

What carries the argument

Emergent network of Josephson junctions intrinsic to the flake

If this is right

  • Quantized Shapiro steps appear under radio-frequency radiation.
  • The height of those steps varies with contact placement, revealing a complex network.
  • Interference patterns match expectations for small junctions and filamentary supercurrent flow.
  • Main features of the pattern remain after nanostructuring and thermal cycling.
  • The setup supplies a route to probe the nature of superconductivity in the AV3Sb5 family.

Where Pith is reading between the lines

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

  • The localized junctions could be used to create functional Josephson elements directly inside these flakes without added patterning steps.
  • Filamentary flow through the network may interact with the topological bands known to exist in kagome lattices.
  • The same emergent junctions are likely to appear in other members of the AV3Sb5 family.

Load-bearing premise

The observed critical current oscillations and Shapiro steps arise exclusively from Josephson junctions rather than alternative mechanisms such as vortex dynamics or geometric effects in the flake geometry.

What would settle it

Absence of quantized Shapiro steps under applied radio-frequency radiation, or persistence of the oscillations when the sample is warmed above its critical temperature.

Figures

Figures reproduced from arXiv: 2510.09777 by Andrea Capa Salinas, Chuan Li, Kaveh Lahabi, Marieke Altena, Matthijs Rog, Milan P. Allan, Stephen D. Wilson, Tycho J. Blom.

Figure 1
Figure 1. Figure 1: Josephson junctions in unstructured Kagome [PITH_FULL_IMAGE:figures/full_fig_p002_1.png] view at source ↗
Figure 2
Figure 2. Figure 2: Non-integer Shapiro steps. a, Shapiro response of flake to irradiation of 600 MHz frequency, measured at 1.5K. The normalized voltage scale shows steps at non￾integer multiples of   . Inset shows the four-probe measurement configuration. b, The same measurement repeated, but now the current and voltage leads are switched, as shown in the inset. The Shapiro steps occur at perfect integers. c, Sketch of a … view at source ↗
Figure 3
Figure 3. Figure 3: Supercurrent interference study using current confinement and various components of the magnetic field. a OOP interference pattern. b IP interference pattern. c Resistance-temperature characteristic of the device used in the interference patterns. The device has a highly inhomogeneous superconducting transition. d Image of the device studied. Using FIB milling, a bar of width 3.2 μm is structured, strongly… view at source ↗
read the original abstract

Materials with a Kagome lattice are intensely studied because they host exotic states that combine strong correlations and topology. Recently, critical current oscillations were observed in an unstructured flake of CsV3Sb5 . In this work, we show that the origin of these oscillations is a network of Josephson junctions intrinsic to the flake that emerges below its critical temperature. Under radio-frequency radiation, we observe quantized Shapiro steps. The sensitivity of the step height to the contact placement indicates a complex network of junctions. By performing interference studies along multiple field directions, we demonstrate that the interference effects are a result of small junctions and filamentary supercurrent flow. Upon nanostructuring the flake, prominent features of the interference pattern are preserved, illustrating the localized nature of these junctions and their stability to thermal cycles. These results pave the way for determining the exact nature of superconductivity in the AV3Sb5 family.

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

1 major / 2 minor

Summary. The manuscript reports experimental observations of critical current oscillations in unstructured flakes of the kagome superconductor CsV3Sb5. The authors interpret these as arising from an emergent intrinsic network of Josephson junctions that forms below the critical temperature. Supporting data include quantized Shapiro steps under RF radiation whose heights depend on contact placement, multi-directional magnetic field interference patterns indicating small junctions and filamentary supercurrent paths, and preservation of key interference features after nanostructuring the flake.

Significance. If the interpretation is correct, the result is significant for the study of superconductivity in the AV3Sb5 family, as it identifies a natural mechanism for realizing Josephson junction networks in these correlated kagome materials without artificial fabrication. The work is strengthened by multiple consistent experimental signatures (Shapiro steps, contact sensitivity, multi-axis interference, and post-nanostructuring stability) that provide a reproducible basis for the claim and could enable new probes of exotic states or device applications.

major comments (1)
  1. [Interference studies section] Interference studies section: The central claim requires that the critical current oscillations and multi-directional interference arise exclusively from the emergent JJ network rather than vortex dynamics, pinning, or geometric current-path effects in the flake. No quantitative modeling, simulation, or control experiment is presented that compares the observed oscillation periods or pattern symmetries against predictions from these alternatives, leaving the exclusivity of the JJ interpretation as a load-bearing but untested element.
minor comments (2)
  1. [Abstract] Abstract: The statement that 'prominent features of the interference pattern are preserved' after nanostructuring would benefit from specifying which features (e.g., period, amplitude, or specific lobes) and providing quantitative metrics such as percentage retention or field-range overlap.
  2. [Experimental methods] Methods or experimental details: The RF radiation frequency, power range, and temperature at which Shapiro steps were measured should be stated explicitly to facilitate reproduction and comparison with standard JJ behavior.

Simulated Author's Rebuttal

1 responses · 0 unresolved

We thank the referee for the positive assessment of our work and the constructive feedback. We address the major comment below and outline the revisions we will make.

read point-by-point responses

  1. Referee: [Interference studies section] Interference studies section: The central claim requires that the critical current oscillations and multi-directional interference arise exclusively from the emergent JJ network rather than vortex dynamics, pinning, or geometric current-path effects in the flake. No quantitative modeling, simulation, or control experiment is presented that compares the observed oscillation periods or pattern symmetries against predictions from these alternatives, leaving the exclusivity of the JJ interpretation as a load-bearing but untested element.

    Authors: We agree that a direct quantitative comparison to alternative models would strengthen the exclusivity of the JJ-network interpretation. However, several of our observations are inconsistent with vortex dynamics, pinning, or purely geometric current-path effects. Quantized Shapiro steps under RF drive are a direct manifestation of the AC Josephson effect and are not expected from vortex motion in a uniform film. The strong dependence of step height on contact placement further indicates a spatially distributed network rather than a single geometric constriction. Finally, the multi-directional interference patterns remain after the flake is nanostructured, which would be expected to alter large-scale current paths or pinning landscapes but leaves localized junctions intact. We will add a dedicated paragraph in the discussion section that explicitly contrasts these signatures with the expected behavior under vortex or geometric scenarios, thereby clarifying why the JJ-network picture is the most consistent with the full data set. Full micromagnetic simulations lie outside the scope of the present experimental study. revision: partial

Circularity Check

0 steps flagged

No significant circularity: purely experimental observations with no derivations or self-referential modeling

full rationale

The paper reports direct experimental measurements on CsV3Sb5 flakes, including critical current oscillations, Shapiro steps under RF radiation, multi-directional interference, and preservation of features after nanostructuring. No equations, fitted parameters, predictions, or derivations are present that could reduce to inputs by construction. Claims rest on observed data and control experiments rather than any self-definitional, fitted-input, or self-citation load-bearing steps. This is a standard experimental study self-contained against external benchmarks, warranting a score of 0.

Axiom & Free-Parameter Ledger

0 free parameters · 2 axioms · 0 invented entities

Experimental paper; no free parameters or invented entities are introduced in the abstract. Relies on standard assumptions of Josephson junction physics and superconducting interference.

axioms (2)
  • standard math Quantized Shapiro steps under RF radiation indicate Josephson junction behavior
    Invoked in abstract as confirmation of junction network
  • domain assumption Interference patterns along multiple field directions reflect filamentary supercurrent through small junctions
    Central to interpreting the data as junction network rather than uniform superconductivity

pith-pipeline@v0.9.0 · 5712 in / 1221 out tokens · 28838 ms · 2026-05-18T08:03:34.452386+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. Nonintegral Flux Trapping in Frustrated Josephson Networks of Triplet Superconductors

    cond-mat.supr-con 2026-04 unverdicted novelty 6.0

    Anisotropic Josephson couplings in triplet superconductor networks produce frustrated d-vector textures that trap nonintegral flux, including pi-flux above a critical antisymmetric coupling strength.

Reference graph

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50 extracted references · 50 canonical work pages · cited by 1 Pith paper

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