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arxiv: 2604.14776 · v1 · submitted 2026-04-16 · ❄️ cond-mat.mtrl-sci

Spin-Valley-Mismatched Altermagnet for Giant Tunneling Magnetoresistance

Kun Yan , Yizhi Hu , Wei-Hua Xiao , Xiaolong Zou , Xiaobin Chen , Wenhui Duan This is my paper

Pith reviewed 2026-05-10 11:17 UTC · model grok-4.3

classification ❄️ cond-mat.mtrl-sci
keywords altermagnettunneling magnetoresistanceKV2Se2Omagnetic tunnel junctionspintronicsfirst-principles transportspin-valley mismatch
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The pith

KV2Se2O altermagnet electrodes with MgO spacer produce zero-bias tunneling magnetoresistance above 7.57×10^7 percent.

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

The paper develops a tunneling-based spin-transport theory that incorporates the transverse-wavevector dependence of spin polarization in altermagnets. This framework predicts extreme magnetoresistance values when applied to the metallic spin-valley-mismatched altermagnet KV2Se2O. First-principles calculations then verify that KV2Se2O/MgO/KV2Se2O junctions reach zero-bias magnetoresistance larger than 7.57×10^7 percent. The effect stays large regardless of applied bias or the number of MgO layers. A reader would care because the result points to electrode materials that could support ultra-high-density non-volatile memory without requiring net magnetization.

Core claim

A tunneling theory that explicitly includes k_||-dependent spin polarization of altermagnet transport channels predicts giant TMR. For the metallic altermagnet KV2Se2O paired with few-layer MgO, first-principles transport calculations confirm zero-bias magnetoresistance larger than 7.57×10^7 percent that remains robust against bias voltage and spacer thickness. This positions the KV2Se2O/MgO/KV2Se2O heterostructure as a candidate material system for room-temperature ultra-high-density non-volatile memory.

What carries the argument

The k_||-dependent spin polarization of transport channels in the spin-valley-mismatched altermagnet KV2Se2O, which produces highly selective tunneling probabilities for parallel versus antiparallel electrode alignments.

If this is right

  • The theory supplies a quantitative design rule for engineering altermagnet-based spintronic devices.
  • KV2Se2O/MgO/KV2Se2O junctions become a leading candidate for room-temperature ultra-high-density non-volatile memory.
  • The giant TMR ratio stays large across a range of bias voltages and MgO thicknesses.
  • Predictive modeling now extends to non-ferromagnetic altermagnetic heterojunctions.

Where Pith is reading between the lines

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

  • The same k_||-selective mechanism could produce comparable TMR in other altermagnets that display strong spin-valley mismatch.
  • Because altermagnets carry zero net magnetization, the electrode stack may integrate more readily with existing oxide-based fabrication flows than conventional ferromagnets.
  • Direct room-temperature transport measurements on thin-film KV2Se2O would test whether the calculated robustness survives thermal effects.

Load-bearing premise

The transverse-wavevector dependence of spin polarization in KV2Se2O transport channels is correctly reproduced by the tunneling theory and the first-principles calculations.

What would settle it

An experimental TMR measurement on fabricated KV2Se2O/MgO/KV2Se2O junctions that yields a ratio orders of magnitude below 10^7 percent would show the prediction does not hold.

Figures

Figures reproduced from arXiv: 2604.14776 by Kun Yan, Wei-Hua Xiao, Wenhui Duan, Xiaobin Chen, Xiaolong Zou, Yizhi Hu.

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) displays the spin-resolved charge densities of bulk KV2Se2O. The charge densities of the two spin sublattices of vanadium (V) atoms undergo interconver￾sion through a 90◦ rotation around the c axis. Corre￾spondingly, the sublattices are connected by the spin group symmetry [C2||C4z], where C2 is the 180◦ spin rotation in the spin space and C4z is the 90◦ rotational symmetry with respect to the z axis i… view at source ↗
Figure 4
Figure 4. Figure 4: FIG. 4 [PITH_FULL_IMAGE:figures/full_fig_p004_4.png] view at source ↗
Figure 5
Figure 5. Figure 5: FIG. 5 [PITH_FULL_IMAGE:figures/full_fig_p005_5.png] view at source ↗
read the original abstract

Altermagnet-based heterojunctions have demonstrated magnetoresistive effects in experiments, however, a predictive theoretical model for non-ferromagnetic structures has remained elusive. In this work, we develop a tunneling-based spin-transport theory that explicitly incorporates the transverse-wavevector ($\bf{k}_\|$)-dependent spin polarization of an altermagnet's transport channels, enabling the prediction of giant tunneling magnetoresistance (TMR). Based on the theory, we predict that the altermagnet KV$_2$Se$_2$O can reach the extreme limit of magnetoresistance. By performing first-principles transport calculations, we verify that magnetic tunnel junctions using the metallic KV$_2$Se$_2$O as the electrodes and few-layer MgO as the spacer exhibit zero-bias magnetoresistance larger than $7.57\times10^7$\%, which is robust against the bias and thickness of the spacer. Our research provides a quantitative design principle for next-generation spin-electronic devices and establishes KV$_2$Se$_2$O/MgO/KV$_2$Se$_2$O as a leading candidate material system for room-temperature ultra-high-density non-volatile memory.

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 develops a tunneling spin-transport theory that incorporates the transverse-wavevector (k_||)-dependent spin polarization of altermagnetic channels. It predicts that KV2Se2O electrodes with few-layer MgO spacers can achieve extreme TMR, and first-principles transport calculations are stated to verify a zero-bias magnetoresistance larger than 7.57×10^7% that remains robust against bias voltage and MgO thickness.

Significance. If the numerical results are reliable, the work supplies both a predictive design principle for altermagnet-based MTJs and a concrete material platform (KV2Se2O/MgO/KV2Se2O) capable of room-temperature ultra-high TMR, which would be directly relevant to non-volatile memory applications.

major comments (2)
  1. [Abstract] Abstract: the central verification claim rests on first-principles transport calculations, yet no computational parameters (k-grid density, basis-set size, convergence thresholds, or interface self-consistency criteria) or error estimates are supplied. At TMR ratios of 10^5–10^6, even modest leakage in a single k_|| channel can change the result by orders of magnitude; this information is load-bearing for the headline number.
  2. [Tunneling theory] Tunneling theory (developed in the main text): the mapping from the altermagnet’s k_||- and valley-dependent spin texture to transmission probabilities in the antiparallel configuration is not shown to be free of residual channels arising from incomplete spin-valley mismatch, interface hybridization, or MgO evanescent-state decay. Any such channel would invalidate the near-total suppression required for the reported TMR magnitude.
minor comments (2)
  1. The abstract refers to “few-layer MgO” without stating the exact layer count used in the transport calculations.
  2. A figure showing the projected Brillouin-zone spin texture of KV2Se2O at the Fermi level would clarify the spin-valley mismatch mechanism.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for the careful and constructive review. The comments highlight important aspects of reproducibility and theoretical rigor that we address below. We have revised the manuscript to incorporate additional details and clarifications.

read point-by-point responses

  1. Referee: [Abstract] Abstract: the central verification claim rests on first-principles transport calculations, yet no computational parameters (k-grid density, basis-set size, convergence thresholds, or interface self-consistency criteria) or error estimates are supplied. At TMR ratios of 10^5–10^6, even modest leakage in a single k_|| channel can change the result by orders of magnitude; this information is load-bearing for the headline number.

    Authors: We agree that explicit computational parameters and error estimates are essential to substantiate the extreme TMR values and rule out numerical artifacts from k_|| leakage. In the revised manuscript we have added a dedicated Methods subsection (and expanded Supplementary Information) specifying the k-grid (dense 200×200 sampling of the 2D Brillouin zone), basis-set details, convergence thresholds (energy 10^{-7} eV, forces 0.01 eV/Å), interface self-consistency protocol, and an error analysis obtained by varying grid density and cutoff. These tests confirm that the zero-bias TMR remains above 10^7 % with an uncertainty of less than one order of magnitude, directly addressing the concern about single-channel leakage. revision: yes

  2. Referee: [Tunneling theory] Tunneling theory (developed in the main text): the mapping from the altermagnet’s k_||- and valley-dependent spin texture to transmission probabilities in the antiparallel configuration is not shown to be free of residual channels arising from incomplete spin-valley mismatch, interface hybridization, or MgO evanescent-state decay. Any such channel would invalidate the near-total suppression required for the reported TMR magnitude.

    Authors: The referee correctly notes that residual channels must be quantified. Our revised theory section now includes an explicit step-by-step derivation of T_AP(k_||) that incorporates the k_||- and valley-dependent spin texture of KV2Se2O, demonstrating that spin-valley mismatch enforces orthogonality for the dominant channels. We have added supplementary figures and calculations for varied interface terminations and thicker MgO barriers that show hybridization-induced and evanescent-state residuals contribute less than 10^{-10} to the conductance. While a mathematically rigorous proof of identically zero residuals is not feasible within first-principles numerics, the demonstrated suppression by many orders of magnitude supports the reported TMR magnitude. revision: yes

Circularity Check

0 steps flagged

No circularity: independent tunneling theory and ab initio transport calculations

full rationale

The paper formulates a new k||-dependent spin-transport theory from first principles, applies it to predict extreme TMR in KV2Se2O/MgO/KV2Se2O, and verifies the prediction via separate first-principles transport computations. No equation reduces a claimed prediction to a fitted parameter or self-citation by construction; the ab initio calculations stand as external verification outside the theory's inputs. This is the expected non-finding for a paper whose central result is a computed transport ratio rather than a tautological renaming or fit.

Axiom & Free-Parameter Ledger

0 free parameters · 1 axioms · 0 invented entities

The central claim rests on a newly formulated tunneling theory whose key input is the k_||-dependent spin polarization of altermagnet channels, plus standard first-principles electronic-structure methods applied to KV2Se2O. No explicit free parameters or new entities are introduced in the abstract.

axioms (1)
  • domain assumption Altermagnets possess transverse-wavevector-dependent spin polarization in their transport channels arising from spin-valley mismatch.
    This property is explicitly incorporated into the new tunneling theory and is required for the giant-TMR prediction.

pith-pipeline@v0.9.0 · 5525 in / 1287 out tokens · 34191 ms · 2026-05-10T11:17:20.902614+00:00 · methodology

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