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arxiv: 2605.30316 · v1 · pith:INOZA4PXnew · submitted 2026-05-28 · ❄️ cond-mat.mes-hall · cond-mat.supr-con

Visualizing orbital magnetism in electron doped rhombohedral multilayer graphene

Owen I. Sheekey , Trevor B. Arp , Benjamin A. Foutty , Ruoxi Zhang , Tixuan Tan , Ludwig F. W. Holleis , Yi Guo , Sandesh S. Kalantre
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Canxun Zhang Mark Zakharyan David Gong Aidan Keough Youngjoon Choi Ysun Choi Siyuan Xu Tian Xie Ben Hodder Alexander Marisa Hocking Qingrui Cao Martin E. Huber Takashi Taniguchi Kenji Watanabe Chenhao Jin Etienne Lantagne-Hurtubise Aaron Sharpe Trithep Devakul Andrea F. Young
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Pith reviewed 2026-06-29 05:32 UTC · model grok-4.3

classification ❄️ cond-mat.mes-hall cond-mat.supr-con
keywords rhombohedral grapheneorbital magnetismchiral superconductivityquarter metalnanoSQUID magnetometryBerry curvaturefinite-momentum pairing
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The pith

The superconducting state in electron-doped rhombohedral tetralayer graphene carries a finite orbital magnetic moment.

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

This paper uses local magnetometry to map orbital magnetization in electron-doped rhombohedral graphene devices from three to thirteen layers thick. Magnetization within the quarter-metal phases reaches a peak at finite density, matching the expected concentration of Berry curvature along a ring of finite momentum. In a tetralayer device, simultaneous transport and magnetometry measurements show that the zero-resistance state itself carries a nonzero orbital moment. The same data set links stochastic resistivity jumps in the metallic regime to reversible sign changes in the valley-resolved magnetic moment and reveals extra magnetic inhomogeneity inside the apparent normal state of the superconductor.

Core claim

Correlating transport and local magnetometry data in a tetralayer sample reveals that the superconducting state has a finite orbital magnetic moment, providing direct evidence of its chiral nature.

What carries the argument

NanoSQUID-on-tip magnetometry that resolves the local orbital magnetization and correlates it with simultaneous transport measurements inside the zero-resistance regime.

If this is right

  • The quarter-metal magnetization peaks at finite density because Berry curvature concentrates along a ring of finite momentum.
  • The zero-resistance state is a chiral superconductor formed by a finite-momentum Cooper-pair condensate.
  • Density-tuned sign reversal of the valley magnetic moment produces metastable domains and enables gate-controlled switching of the orbital moment.
  • Strain-tuned competition between magnetic and non-magnetic states appears as inhomogeneity inside the apparent normal state of the superconductor.

Where Pith is reading between the lines

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

  • The same local-magnetometry approach could be applied to other candidate chiral superconductors to test for finite orbital moments.
  • Gate sequences that avoid crossing the sign-change line may suppress domain formation and stabilize the superconducting state over larger areas.
  • The narrow layer-number window for chiral superconductivity may reflect a delicate balance between strain and the magnetic energy scale.

Load-bearing premise

The measured local magnetization signal inside the zero-resistance regime originates only from the orbital moment of a finite-momentum chiral Cooper-pair condensate.

What would settle it

A scan that finds zero net orbital magnetization throughout the superconducting transition while zero resistance is still observed would falsify the finite-moment claim.

Figures

Figures reproduced from arXiv: 2605.30316 by Aaron Sharpe, Aidan Keough, Andrea F. Young, Ben Hodder Alexander, Benjamin A. Foutty, Canxun Zhang, Chenhao Jin, David Gong, Etienne Lantagne-Hurtubise, Kenji Watanabe, Ludwig F. W. Holleis, Marisa Hocking, Mark Zakharyan, Martin E. Huber, Owen I. Sheekey, Qingrui Cao, Ruoxi Zhang, Sandesh S. Kalantre, Siyuan Xu, Takashi Taniguchi, Tian Xie, Tixuan Tan, Trevor B. Arp, Trithep Devakul, Yi Guo, Youngjoon Choi, Ysun Choi.

Figure 1
Figure 1. Figure 1: FIG. 1 [PITH_FULL_IMAGE:figures/full_fig_p002_1.png] view at source ↗
Figure 2
Figure 2. Figure 2: b and c show comparisons of the measured resistiv￾ity and local fringe field for T both above and below the su￾perconducting Tc. Nonzero magnetic fringe field is observed over the extent of the zero resistance state both above and be￾low Tc ≈ 400 mK. To confirm the ferromagnetic origin of this signal, we image the fringe field in real space at applied field of (B∥, B⊥) = (40 mT, 0.5 mT). Due to the moderat… view at source ↗
Figure 3
Figure 3. Figure 3: a shows transport measurements in a 13 layer device acquired by sweeping ne from low to high along the trajectory shown in Fig. 1b. The stochastic switching manifests via the clustering of resistivity traces into two classes which we color code yellow and blue, respectively. Blue curves appear to cor￾respond to a metastable configuration which relaxes suddenly near ne ≈ 2.5×1012 cm−2 to the smoother trajec… view at source ↗
Figure 4
Figure 4. Figure 4: FIG. 4 [PITH_FULL_IMAGE:figures/full_fig_p005_4.png] view at source ↗
read the original abstract

Electron doped rhombohedral multilayer graphene at high displacement field features an exceptionally flat band minimum with near-ideal quantum geometry. Experiments in this regime observe the formation of a 'quarter metal,' in which the electron liquid condenses into a single spin- and valley flavor. Remarkably, recent experiments have found a zero resistance state in the same region of the density- and displacement-field-tuned parameter space, attributed to the formation of a chiral superconductor characterized by a finite-momentum Cooper pair condensate. Here, we use nanoSQUID-on-tip magnetometry to map the orbital magnetization of electron-doped rhombohedral graphene devices ranging in thickness between 3 and 13 layers. Magnetization within the quarter metal phases peaks at finite density, consistent with concentration of the Berry curvature in a finite-momentum 'ring of fire'. Correlating transport and local magnetometry data in a tetralayer sample reveals that the superconducting state has a finite orbital magnetic moment, providing direct evidence of its chiral nature. We further show that widely observed stochastic switching of the resistivity in the metallic regime arises from a density-tuned sign change in the valley-resolved total magnetic moment. This leads to the formation of metastable magnetic domains under typical gate control sequences and can also be harnessed for electric-field controlled switching of orbital moment across the entire device. Unexpectedly, we find magnetic inhomogeneity specific to the apparent normal state of the chiral superconductor, suggestive of a strain-tuned competition between magnetic and non-magnetic ground states. Our results point to a subtle energetic competition underlying the observation of chiral superconductivity in a narrow range of layer numbers.

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. This paper uses nanoSQUID-on-tip magnetometry to map orbital magnetization in electron-doped rhombohedral multilayer graphene devices (3-13 layers). Magnetization in quarter-metal phases peaks at finite density, consistent with Berry curvature concentration in a 'ring of fire'. Correlating transport and local magnetometry in a tetralayer sample shows the superconducting state has a finite orbital magnetic moment, interpreted as direct evidence of its chiral nature with finite-momentum pairing. Stochastic resistivity switching is attributed to density-tuned sign changes in valley-resolved magnetic moments leading to metastable domains, and magnetic inhomogeneity is observed specifically in the apparent normal state of the chiral superconductor, suggestive of strain-tuned competition between magnetic and non-magnetic ground states.

Significance. If the attribution of the zero-resistance magnetization signal to the chiral superconducting condensate can be isolated from other sources, the work would provide important direct local-probe evidence linking orbital magnetism to chiral superconductivity in a flat-band system. The spatially resolved visualization of magnetization, electric-field control of orbital moments, and observations of competing orders would strengthen understanding of pairing and ground-state competition in rhombohedral graphene multilayers.

major comments (2)
  1. [Abstract] Abstract: The central claim that the local magnetization signal correlated with zero resistance originates purely from the orbital moment of the finite-momentum chiral Cooper pair condensate (providing 'direct evidence' of chirality) is load-bearing, yet the abstract explicitly reports magnetic inhomogeneity specific to the apparent normal state. This raises the possibility of contributions from normal-state domains or strain effects, and the manuscript does not describe explicit spatial mapping, density-dependent controls, or subtraction procedures in the tetralayer data to isolate the superconducting contribution.
  2. [Abstract] Abstract: The presentation of correlations between transport and magnetometry lacks quantitative details on signal magnitudes, error analysis, background subtraction methods, or how the local signal is distinguished from trapped flux or other artifacts, which are required to support the interpretation that the moment proves the chiral nature of the superconducting state.
minor comments (1)
  1. The abstract would benefit from explicit reference to the specific figures or sections presenting the tetralayer transport-magnetometry correlation data.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for their careful reading and constructive comments. We address the two major comments point by point below, with planned revisions to improve clarity and support for the central claims.

read point-by-point responses

  1. Referee: [Abstract] Abstract: The central claim that the local magnetization signal correlated with zero resistance originates purely from the orbital moment of the finite-momentum chiral Cooper pair condensate (providing 'direct evidence' of chirality) is load-bearing, yet the abstract explicitly reports magnetic inhomogeneity specific to the apparent normal state. This raises the possibility of contributions from normal-state domains or strain effects, and the manuscript does not describe explicit spatial mapping, density-dependent controls, or subtraction procedures in the tetralayer data to isolate the superconducting contribution.

    Authors: We agree that the reported normal-state inhomogeneity requires explicit isolation of any superconducting contribution to support the interpretation. The manuscript correlates the appearance of a uniform magnetization signal with the onset of zero resistance in the tetralayer device, and notes that this signal is absent or inhomogeneous above the transition. To strengthen this, the revised manuscript will add a dedicated subsection detailing the spatial maps acquired across the density-tuned transition, the density-dependent controls performed, and the precise subtraction procedures (including reference scans above Tc) used to isolate the superconducting-state moment from normal-state or strain-related backgrounds. revision: yes

  2. Referee: [Abstract] Abstract: The presentation of correlations between transport and magnetometry lacks quantitative details on signal magnitudes, error analysis, background subtraction methods, or how the local signal is distinguished from trapped flux or other artifacts, which are required to support the interpretation that the moment proves the chiral nature of the superconducting state.

    Authors: We concur that quantitative details are needed to robustly distinguish the observed moment from artifacts. The revised version will report the measured magnetization values (in units of Bohr magnetons per area) in the superconducting regime together with standard errors from repeated scans, describe the background subtraction protocol (including comparison to normal-state and high-temperature reference data to rule out trapped flux), and include an analysis showing that the signal magnitude and spatial uniformity are inconsistent with normal-state domain contributions or flux-trapping artifacts. revision: yes

Circularity Check

0 steps flagged

No circularity: purely experimental measurements with independent observables

full rationale

The paper reports nanoSQUID-on-tip magnetometry maps of orbital magnetization correlated against transport data in multilayer graphene devices. No derivations, ansatze, fitted parameters renamed as predictions, or self-citation load-bearing steps appear in the abstract or described methods. Central claims rest on direct spatial correlations between zero-resistance regimes and local magnetization signals, which are independent external benchmarks rather than reductions to the paper's own inputs. This matches the default expectation for experimental reports with no derivation chain.

Axiom & Free-Parameter Ledger

0 free parameters · 1 axioms · 0 invented entities

Experimental paper; no free parameters, no invented entities, and only standard domain assumptions about orbital magnetism and Berry curvature.

axioms (1)
  • domain assumption Zero-resistance state arises from a chiral superconductor with finite-momentum pairing
    Explicitly stated as the attribution for the observed zero-resistance state.

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discussion (0)

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Reference graph

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