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arxiv: 2606.29140 · v1 · pith:PKJWMTPYnew · submitted 2026-06-28 · ❄️ cond-mat.mtrl-sci · cond-mat.mes-hall· cond-mat.str-el· cond-mat.supr-con

Real-space identification of distinct magnetic configurations in a candidate d-wave altermagnet

Jin-Cheng Gu , Mingzhe Hu , Ziyin Song , Lihan Wang , Lihong Wang , Junming Zhang , Jiali Zhao , Hang Li
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Shifeng Jin Xin-Ding Zhang Genfu Chen Hongming Weng Zhongxu Wei Tian Qian
This is my paper

Pith reviewed 2026-06-30 03:19 UTC · model grok-4.3

classification ❄️ cond-mat.mtrl-sci cond-mat.mes-hallcond-mat.str-elcond-mat.supr-con
keywords altermagnetismKV2Se2Ospin-polarized STMquasiparticle interferencemagnetic configurationsd-waveantiferromagnetismspin splitting
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The pith

KV2Se2O hosts both C-type d-wave altermagnetic and G-type antiferromagnetic orders with similar spin-split bands.

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

The paper establishes that the candidate d-wave altermagnet KV2Se2O contains regions of two distinct real-space magnetic configurations. Spin-polarized scanning tunneling microscopy maps a checkerboard antiparallel spin texture in the V2O layer and its interlayer arrangement, revealing both C-type order (d-wave altermagnetic) and G-type order (conventional antiferromagnetic). These orders produce nearly identical momentum-dependent spin splitting when examined at the single-layer level. A sympathetic reader cares because the result explains why momentum-space data alone left the magnetic origin ambiguous and demonstrates that the material supports multiple nearly degenerate magnetic states rather than a single order.

Core claim

In KV2Se2O, spin-polarized scanning tunnelling microscopy combined with magnetic-field-dependent quasiparticle interference imaging determines the magnetic configuration at the atomic scale. Spin-resolved quasiparticle interference reveals a checkerboard-like antiparallel spin texture within the V2O layer and determines its interlayer spin arrangement across unit-cell step edges. Both C-type and G-type magnetic configurations are identified, which generate similar spin-split electronic structures at the single-layer level but correspond to d-wave altermagnetic and conventional antiferromagnetic orders, respectively.

What carries the argument

Spin-polarized STM with magnetic-field-dependent quasiparticle interference that resolves the checkerboard antiparallel spin texture in the V2O layer and the interlayer spin stacking across step edges.

If this is right

  • Momentum-space spin splitting can arise from either d-wave altermagnetic or conventional antiferromagnetic real-space order.
  • A direct link exists between the observed momentum-dependent spin splitting and the identified real-space magnetic configurations.
  • The material exhibits a complex magnetic landscape arising from nearly degenerate magnetic states.
  • A framework is provided for identifying the microscopic origin of spin-split electronic structures in altermagnetic materials.

Where Pith is reading between the lines

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

  • Momentum-space probes alone may be insufficient to confirm altermagnetism in other candidate materials that also host multiple nearly degenerate orders.
  • The near degeneracy between orders suggests that strain, doping, or external fields could be used to select one configuration over the other.
  • Real-space imaging techniques may need to become standard for resolving ambiguities in altermagnet candidates where single-layer spin splitting looks similar for different orders.

Load-bearing premise

The surface spin textures and interlayer spin arrangements seen by STM directly reflect the bulk magnetic configurations without significant surface reconstruction or imaging artifacts.

What would settle it

Finding only a single magnetic configuration type or spin textures whose interlayer stacking fails to match the expected C-type or G-type patterns would falsify the claim that both orders coexist.

read the original abstract

Altermagnetism is an emerging class of magnetic order characterized by momentum-dependent spin-split electronic structures despite vanishing net magnetization. Although momentum-space signatures consistent with altermagnetism have been reported in a growing number of materials, their relationship to the underlying real-space magnetic configurations remains incompletely understood, because similar spin-split electronic structures can arise from distinct magnetic orders. In the candidate d-wave altermagnet KV2Se2O, the magnetic origin of the observed momentum-dependent spin splitting has remained controversial. Here, we employ spin-polarized scanning tunnelling microscopy combined with magnetic-field-dependent quasiparticle interference imaging to determine the magnetic configuration of KV2Se2O at the atomic scale. Spin-resolved quasiparticle interference reveals a checkerboard-like antiparallel spin texture within the V2O layer and determines its interlayer spin arrangement across unit-cell step edges. Remarkably, we identify both C-type and G-type magnetic configurations, both of which generate similar spin-split electronic structures at the single-layer level but correspond to d-wave altermagnetic and conventional antiferromagnetic orders, respectively. These observations reveal a complex magnetic landscape arising from nearly degenerate magnetic states. Our results establish a direct connection between momentum-space spin splitting and real-space magnetic order, providing a framework for identifying the microscopic origin of spin-split electronic structures in altermagnetic materials.

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 / 2 minor

Summary. The manuscript reports spin-polarized STM combined with magnetic-field-dependent QPI imaging on KV2Se2O. It claims to resolve atomic-scale checkerboard antiparallel spin textures within the V2O layer and interlayer spin arrangements across unit-cell steps, thereby identifying both C-type (d-wave altermagnetic) and G-type (conventional antiferromagnetic) magnetic configurations that produce similar single-layer spin-split electronic structures.

Significance. If the surface-derived assignments are shown to represent bulk order, the work would establish a direct real-space to momentum-space connection for altermagnetic signatures and demonstrate the existence of nearly degenerate magnetic states, addressing an open question in the field.

major comments (2)
  1. [Abstract and STM/QPI results] The central claim that the observed surface spin textures and step-edge arrangements identify bulk C-type and G-type orders (Abstract and results sections) rests on the untested assumption that STM images map directly to bulk magnetic configurations without surface relaxation or reconstruction; the manuscript provides no surface-versus-bulk DFT comparisons or cross-checks against bulk-sensitive probes such as neutron diffraction.
  2. [Abstract and discussion of electronic structures] The assertion that both C- and G-type configurations generate similar spin-split electronic structures at the single-layer level (Abstract) is load-bearing for distinguishing altermagnetic from conventional AF order, yet the text does not include explicit single-layer band-structure calculations or quantitative comparison of the splitting magnitudes.
minor comments (2)
  1. [Abstract and methods] The abstract and methods do not report quantitative error analysis, tip-polarization calibration details, or statistics on the relative occurrence of C- versus G-type regions, which would strengthen the claim of a 'complex magnetic landscape'.
  2. [Figure captions] Figure captions and text should explicitly state the magnetic field values and bias voltages used for the QPI maps to allow reproducibility assessment.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for the constructive feedback on our manuscript. We address each major comment below and will revise the manuscript to strengthen the presentation of our results while maintaining scientific accuracy.

read point-by-point responses

  1. Referee: [Abstract and STM/QPI results] The central claim that the observed surface spin textures and step-edge arrangements identify bulk C-type and G-type orders (Abstract and results sections) rests on the untested assumption that STM images map directly to bulk magnetic configurations without surface relaxation or reconstruction; the manuscript provides no surface-versus-bulk DFT comparisons or cross-checks against bulk-sensitive probes such as neutron diffraction.

    Authors: We agree that the manuscript does not include surface-versus-bulk DFT comparisons or data from bulk-sensitive probes such as neutron diffraction. Our assignments of C-type and G-type configurations are derived from atomic-scale spin textures within the V2O layer and the interlayer spin arrangements observed across unit-cell step edges. While these observations are consistent with the expected bulk orders reported in prior literature on KV2Se2O, we acknowledge that surface relaxation effects cannot be ruled out without additional calculations. In the revised manuscript, we will add an explicit discussion of this limitation, clarify that the identified configurations are surface-derived, and moderate the language in the abstract and results sections to avoid implying direct bulk identification without further evidence. revision: yes

  2. Referee: [Abstract and discussion of electronic structures] The assertion that both C- and G-type configurations generate similar spin-split electronic structures at the single-layer level (Abstract) is load-bearing for distinguishing altermagnetic from conventional AF order, yet the text does not include explicit single-layer band-structure calculations or quantitative comparison of the splitting magnitudes.

    Authors: The claim in the abstract is based on symmetry arguments and the similarity of the observed QPI patterns for both configurations. However, we agree that the manuscript does not present explicit single-layer band-structure calculations or quantitative comparisons of spin-splitting magnitudes. To address this, the revised version will include new single-layer DFT calculations for both the C-type and G-type magnetic configurations, with direct comparison of the resulting spin-split bands and splitting magnitudes to support the assertion. revision: yes

Circularity Check

0 steps flagged

No circularity: purely experimental STM/QPI imaging study

full rationale

The manuscript reports atomic-scale spin-polarized STM and magnetic-field-dependent QPI measurements on KV2Se2O to assign C-type and G-type magnetic orders. No equations, fitted parameters, or derivations are presented; claims rest on direct imaging of spin textures and step-edge arrangements. No self-citation load-bearing steps, ansatzes, or renamings of known results occur. The work is self-contained against external benchmarks and does not reduce any result to its own inputs by construction.

Axiom & Free-Parameter Ledger

0 free parameters · 1 axioms · 0 invented entities

Experimental work relying on established STM and QPI techniques; no free parameters, new axioms beyond domain standards, or invented entities are introduced.

axioms (1)
  • domain assumption Spin-polarized STM and magnetic-field-dependent QPI faithfully report bulk-like magnetic order without dominant surface effects.
    Interpretation of checkerboard texture and interlayer alignment rests on this standard assumption of the technique.

pith-pipeline@v0.9.1-grok · 5832 in / 1105 out tokens · 46935 ms · 2026-06-30T03:19:15.713136+00:00 · methodology

discussion (0)

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Reference graph

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