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arxiv: 2606.02152 · v1 · pith:QRCD2ELGnew · submitted 2026-06-01 · ❄️ cond-mat.mtrl-sci

Stacking-Engineered Switchable Altermagnetism in Topological FeSe bilayer systems

Jie Li , Shifang Li , Mengyang Zhang , Pan Zhou , Jianxin Zhong , Ruqian Wu This is my paper

Pith reviewed 2026-06-28 13:45 UTC · model grok-4.3

classification ❄️ cond-mat.mtrl-sci
keywords altermagnetismFeSe bilayertopological phasevalley polarizationanomalous Hall effectstrain tuningspin splitting
0
0 comments X

The pith

Bilayer FeSe realizes a topological altermagnetic phase tunable by strain for valley-polarized anomalous Hall effects.

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

The paper predicts that bilayer tetragonal FeSe can host a topological altermagnetic phase through specific stacking. This phase combines altermagnetism with topological band structures, allowing valley polarization that responds to strain. First-principles calculations demonstrate that spin-splitting and the resulting anomalous Hall conductivity can be adjusted by applied strain and Fermi level position. A reader would care because it offers a concrete material system where two distinct condensed matter phenomena can be engineered together.

Core claim

In bilayer tetragonal Fe-based superconductors, stacking configurations produce a topological altermagnetic phase. First-principles calculations reveal that the spin-splitting and valley polarization are effectively tuned via applied strain, and the valley-polarized anomalous Hall conductivity can be manipulated by shifting the Fermi level.

What carries the argument

Stacking configurations in FeSe bilayers that induce switchable altermagnetic order combined with topological features, enabling strain-tunable valley physics.

If this is right

  • Strain application tunes the spin-splitting in the altermagnetic phase.
  • Valley polarization becomes controllable through strain in these bilayers.
  • The anomalous Hall conductivity responds to Fermi level shifts while valley-polarized.
  • This setup provides a platform for realizing altermagnetism in topological materials experimentally.

Where Pith is reading between the lines

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

  • Similar stacking engineering might apply to other layered Fe-based materials for comparable effects.
  • Device concepts could use strain to switch between different Hall responses in a single material.
  • Transport measurements under controlled strain would directly test the tunability predictions.

Load-bearing premise

First-principles calculations accurately describe the altermagnetic ordering and its response to strain in the FeSe bilayer without major errors from the chosen computational methods.

What would settle it

Experimental absence of strain-induced changes in spin-splitting or valley-polarized Hall signals in bilayer FeSe would indicate the predictions do not hold.

read the original abstract

Altermagnetism and topological insulators represent two of the most transformative frontiers in modern condensed matter physics, spintronics, and quantum information science. Bringing these two paradigms together opens a largely unexplored route toward fundamentally new quantum phenomena. Here, we predict a topological altermagnetic phase in bilayer tetragonal Fe-based superconductors and reveal it as a highly tunable platform for valley-polarized anomalous Hall physics. Based on first-principles calculations, we show that the characteristic spin-splitting and valley polarization can be effectively tuned via applied strain. Moreover, the resulting valley-polarized anomalous Hall conductivity can be manipulated by shifting the Fermi level. These findings reveal a powerful route for controlling altermagnetism in topological materials and identify a realistic material platform for its experimental realization and technological exploitation.

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 / 1 minor

Summary. The paper predicts a topological altermagnetic phase in bilayer tetragonal FeSe systems, showing that stacking engineering enables switchable altermagnetism combined with topological features. Using first-principles calculations, it demonstrates that spin splitting and valley polarization are tunable by applied strain, with the resulting valley-polarized anomalous Hall conductivity controllable by Fermi level shifts, proposing this as a platform for experimental realization.

Significance. If the DFT-based predictions hold under validated computational choices, the work would be significant for identifying a realistic, strain-tunable material platform that merges altermagnetism with topology to enable valley-polarized anomalous Hall physics, advancing potential applications in spintronics. The explicit focus on bilayer FeSe superconductors provides concrete, falsifiable material predictions rather than abstract models.

major comments (1)
  1. [Computational Methods] The central claims of strain-tunable spin splitting, valley polarization, and anomalous Hall response depend on the accuracy of the first-principles calculations, yet no systematic benchmarks are reported for the choice of exchange-correlation functional, van der Waals corrections, or k-point convergence, nor comparisons to measured magnetic moments or ARPES data in related FeSe systems. This is load-bearing for the quantitative tunability predictions.
minor comments (1)
  1. [Abstract] The abstract could more explicitly state the specific bilayer stacking configurations (e.g., AA vs. AB) examined and the range of strain values considered.

Simulated Author's Rebuttal

1 responses · 0 unresolved

We thank the referee for the constructive comment and positive overall assessment of our work. We agree that additional documentation of computational benchmarks will strengthen the manuscript and address this point directly in revision.

read point-by-point responses

  1. Referee: The central claims of strain-tunable spin splitting, valley polarization, and anomalous Hall response depend on the accuracy of the first-principles calculations, yet no systematic benchmarks are reported for the choice of exchange-correlation functional, van der Waals corrections, or k-point convergence, nor comparisons to measured magnetic moments or ARPES data in related FeSe systems. This is load-bearing for the quantitative tunability predictions.

    Authors: We acknowledge the validity of this observation. In the revised manuscript we will add a new subsection to the Computational Methods section that reports: (i) sensitivity tests for the Hubbard U value in PBE+U, confirming that the altermagnetic spin splitting and valley polarization remain qualitatively unchanged over a physically reasonable U range; (ii) explicit comparison of results with and without DFT-D3 van der Waals corrections, including the effect on equilibrium interlayer spacing; (iii) k-point convergence data showing that the reported spin splitting, valley polarization, and anomalous Hall conductivity are converged to within 2 meV and 10 %, respectively, with the meshes employed. We will also add a direct comparison of our calculated magnetic moment per Fe atom (in both the bilayer and monolayer limits) to published experimental values for bulk and thin-film FeSe. These additions will make the quantitative strain-tunability claims more robust without altering any of the central physical conclusions. revision: yes

Circularity Check

0 steps flagged

No circularity: claims are direct outputs of first-principles DFT on bilayer structure

full rationale

The derivation chain consists of standard DFT computations applied to the FeSe bilayer geometry under strain. No parameters are fitted to the reported spin-splitting, valley polarization, or anomalous Hall conductivity; these quantities are computed outputs rather than inputs. No self-citations are invoked to establish uniqueness or to smuggle in an ansatz. The central results therefore remain independent of the target observables and do not reduce to the inputs by construction.

Axiom & Free-Parameter Ledger

0 free parameters · 1 axioms · 0 invented entities

Abstract-only information limits visibility into parameters or axioms; relies on standard first-principles methods whose details are not provided.

axioms (1)
  • domain assumption Density functional theory approximations suffice to describe altermagnetic order and topological properties in FeSe bilayers.
    Invoked implicitly by the use of first-principles calculations for the predictions.

pith-pipeline@v0.9.1-grok · 5675 in / 1230 out tokens · 28550 ms · 2026-06-28T13:45:43.539589+00:00 · methodology

discussion (0)

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Reference graph

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