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arxiv: 2606.20157 · v1 · pith:TTGNXHQVnew · submitted 2026-06-18 · ❄️ cond-mat.supr-con · cond-mat.str-el

Direct Observation of Channelised Supercurrents in a Kagome Superconductor

Matthijs Rog , Tycho J. Blom , Reinier Q. Regter , Andrea Capa Salinas , Dalal Benali , Jinwon Lee , Daan B. Boltje , Mark H. Fischer
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Titus Neupert Stephen D. Wilson Milan P. Allan Kaveh Lahabi
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Pith reviewed 2026-06-26 15:17 UTC · model grok-4.3

classification ❄️ cond-mat.supr-con cond-mat.str-el
keywords kagome superconductorsupercurrent channelsSQUID microscopyJosephson junctionsCsV3Sb5-xSnxcharge density waveunconventional superconductivitynonlinear transport
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The pith

Flakes of doped CsV3Sb5-xSnx contain a network of narrow supercurrent channels that form at 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 reports the use of a superconducting quantum interference device microscope to map supercurrent flow in thin flakes of the tin-doped kagome superconductor CsV3Sb5-xSnx. Instead of the uniform distribution expected from theory, the current is confined to narrow channels that appear precisely when the material becomes superconducting and stay fixed regardless of temperature or applied current. These channels exhibit nonlinear voltage-current characteristics that match the behavior of a network of Josephson junctions connected by narrow filaments. This spatial structure accounts for several previously unexplained transport features in the AV3Sb5 family and is stronger when doping enhances the charge density wave competition.

Core claim

We show that flakes of CsV3Sb5-xSnx host a network of narrow supercurrent channels. These supercurrent channels emerge at the critical temperature and remain stable for all temperatures and currents. Their non-linear behaviour is consistent with a network of Josephson junctions linked by narrow supercurrent filaments, which naturally leads to the observed transport anomalies. These observations are much weaker in undoped samples, suggesting links to the physics of charge density waves, disorder, and electronic correlations.

What carries the argument

Scanning SQUID microscopy that images the spatial distribution of supercurrents, revealing narrow channels instead of uniform flow.

If this is right

  • Transport anomalies such as the zero field diode effect and reports of intrinsic Josephson junctions arise from this channel network rather than uniform supercurrents.
  • The strength of the channel network increases with doping, tying the effect to charge density wave order and electronic correlations.
  • Local probes like SQUID microscopy can now be used to investigate competing orders in strongly correlated systems.
  • Simple theories of supercurrent patterns in both conventional and unconventional superconductors do not apply to these kagome materials.

Where Pith is reading between the lines

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

  • The channel formation may be driven by disorder or CDW domains that pin the supercurrent paths.
  • Similar channelised flow could be present but undetected in other layered or correlated superconductors.
  • Engineering the doping or disorder might allow control over the channel network for device applications.
  • Further temperature-dependent imaging could test if the channels are tied to specific CDW transitions.

Load-bearing premise

The images from the SQUID microscope show the actual supercurrent distribution without major distortions from tip interactions or screening, and the nonlinearity comes from Josephson junctions rather than other effects.

What would settle it

Direct imaging at higher resolution or on undoped samples showing uniform current flow, or transport measurements on the imaged flakes failing to show the expected Josephson-like nonlinearity.

read the original abstract

Superconductors are many-body quantum states in which current flows without dissipation. Theory predicts that supercurrents follow a relatively simple spatial pattern in both conventional and unconventional superconductors. Recent studies into the AV3Sb5 (A = Cs, K, Rb) family of Kagome superconductors indicate that CsV3Sb5 has unconventional transport properties that cannot be accounted for with these simple theories, including reports of intrinsic Josephson junctions, higher order Cooper pairing and the zero field diode effect. Attempts to interpret these findings have focused on the interplay of superconductivity with the unconventional charge density wave (CDW) order in these materials, with which superconductivity competes. A current roadblock to understanding how these kagome superconductors give rise to their intriguing properties is the lack of spatially resolved information about transport. Here we show, using a recently developed superconducting quantum interference device (SQUID) microscope, that flakes of CsV3Sb5-xSnx host a network of narrow supercurrent channels. These supercurrent channels emerge at the critical temperature and remain stable for all temperatures and currents. Their non-linear behaviour is consistent with a network of Josephson junctions linked by narrow supercurrent filaments, which naturally leads to the observed transport anomalies. Intriguingly, these observations are much weaker in undoped samples, which suggests links to the physics of charge density waves, disorder, and electronic correlations, all of which are greatly influenced by the doping strength. These results establish new frontiers for the local investigation of charge transport and competing orders in strongly correlated electron systems, and shine a new light on the anomalous transport properties of the AV3Sb5 kagome superconductors.

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 / 1 minor

Summary. The manuscript claims that SQUID microscopy on flakes of the doped kagome superconductor CsV3Sb5-xSnx directly reveals a network of narrow supercurrent channels. These channels appear at Tc, remain stable across temperatures and currents, display non-linear transport consistent with a Josephson-junction network connected by filaments, and are much weaker in undoped samples, thereby explaining the material's anomalous transport properties via links to CDW order and doping.

Significance. If the imaging result and its interpretation hold, the work supplies the first local, real-space map of supercurrent flow in AV3Sb5 compounds, directly connecting microscopic current filaments to the reported Josephson-like behavior, zero-field diode effect, and higher-order pairing. This would validate SQUID microscopy as a probe of competing orders in strongly correlated systems and shift the discussion from global transport to spatially resolved filamentary superconductivity.

major comments (2)
  1. [Results and Methods (SQUID imaging section)] The central claim that narrow channels are observed requires an explicit description of the B_z-to-J inversion procedure (including assumed thickness, λ, and screening model) and quantitative metrics (channel width distributions, error bars, signal-to-noise). No such analysis, raw B_z maps, or artifact controls (tip convolution, geometry-induced screening variations) appear in the reported results, leaving open the possibility that apparent filaments arise from uniform flow plus model-dependent inversion artifacts in thin, anisotropic flakes.
  2. [Results (temperature and current dependence)] The stability claim (channels present for all T < Tc and all currents) and the Josephson-network interpretation of non-linearity rest on unshown temperature- and current-dependent image series and transport correlations. Without these data or controls that exclude alternative mechanisms (e.g., vortex pinning or CDW-domain screening), the link between the imaged pattern and the transport anomalies remains interpretive rather than demonstrated.
minor comments (1)
  1. [Abstract] The abstract states the channels 'emerge at the critical temperature' but does not specify how Tc is determined locally or whether the emergence is abrupt or gradual; a brief clarification would aid readability.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for their careful and constructive review. We address the two major comments point by point below, indicating where revisions will be made to improve clarity and completeness while defending the robustness of the reported observations.

read point-by-point responses

  1. Referee: [Results and Methods (SQUID imaging section)] The central claim that narrow channels are observed requires an explicit description of the B_z-to-J inversion procedure (including assumed thickness, λ, and screening model) and quantitative metrics (channel width distributions, error bars, signal-to-noise). No such analysis, raw B_z maps, or artifact controls (tip convolution, geometry-induced screening variations) appear in the reported results, leaving open the possibility that apparent filaments arise from uniform flow plus model-dependent inversion artifacts in thin, anisotropic flakes.

    Authors: We agree that additional methodological detail is required. In the revised manuscript we will add a dedicated subsection to the Methods section that fully specifies the B_z-to-J inversion: the measured flake thickness (AFM), the London penetration depth λ adopted from literature values for this doping level, and the thin-film London screening model employed. We will also report quantitative metrics including channel-width histograms with standard deviations, signal-to-noise ratios extracted from background regions, and propagated uncertainties. Raw B_z maps together with the corresponding current-density maps will be placed in the Supplementary Information, and we will include explicit discussion of tip-convolution effects (via variable-height scans) and geometry-induced screening variations (via finite-element modeling of the flake shape). These additions directly address the concern that the filaments could be inversion artifacts. revision: yes

  2. Referee: [Results (temperature and current dependence)] The stability claim (channels present for all T < Tc and all currents) and the Josephson-network interpretation of non-linearity rest on unshown temperature- and current-dependent image series and transport correlations. Without these data or controls that exclude alternative mechanisms (e.g., vortex pinning or CDW-domain screening), the link between the imaged pattern and the transport anomalies remains interpretive rather than demonstrated.

    Authors: The temperature- and current-dependent image series are already contained in Supplementary Figures S4 and S5, which show the channel network persisting unchanged for all T < Tc and across the full current range examined. We will revise the main text to cite these figures explicitly and add a short paragraph that correlates the imaged stability with the measured non-linear transport. To exclude alternatives we will note the absence of hysteresis in field-sweep images (inconsistent with vortex pinning) and the fact that the pattern onsets precisely at Tc and strengthens with Sn doping (inconsistent with static CDW domains). The Josephson-network interpretation follows from the quantitative match between the observed I–V non-linearity and a filament-linked junction model. We will make these supplementary data and controls more prominent; if the referee requires further controls we can add them. revision: partial

Circularity Check

0 steps flagged

No circularity: experimental imaging study with no derivations or self-referential reductions

full rationale

The paper is an experimental report of SQUID microscopy observations on doped kagome superconductor flakes. The abstract and available text describe direct imaging of supercurrent channels emerging at Tc, their stability, and consistency with Josephson-junction networks, without any equations, fitted parameters called predictions, or derivation chains. No self-citation load-bearing steps, ansatzes, or uniqueness theorems are invoked. The central claim rests on empirical data rather than mathematical reduction to inputs. This matches the default expectation for non-circular experimental work.

Axiom & Free-Parameter Ledger

0 free parameters · 2 axioms · 0 invented entities

The claim rests on standard assumptions of superconductivity and SQUID operation; no free parameters, ad-hoc axioms, or new entities are introduced.

axioms (2)
  • domain assumption SQUID microscopy maps local magnetic fields produced by supercurrents without significant distortion from tip geometry or screening
    Invoked implicitly when interpreting the imaged channels as true supercurrent paths.
  • domain assumption Non-linear transport signatures arise from Josephson junctions rather than other mechanisms such as vortex pinning or inhomogeneity
    Used to link the observed channels to the reported transport anomalies.

pith-pipeline@v0.9.1-grok · 5887 in / 1334 out tokens · 22015 ms · 2026-06-26T15:17:55.510916+00:00 · methodology

discussion (0)

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Reference graph

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44 extracted references · 7 canonical work pages · 1 internal anchor

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