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Real and momentum space analysis of topological phases in 2D d-wave altermagnets
by Manuel Calixto
Submission summary
| Authors (as registered SciPost users): | Manuel Calixto |
| Submission information | |
|---|---|
| Preprint Link: | https://arxiv.org/abs/2602.04854v1 (pdf) |
| Date submitted: | Feb. 5, 2026, 12:08 p.m. |
| Submitted by: | Manuel Calixto |
| Submitted to: | SciPost Physics |
| Ontological classification | |
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| Academic field: | Physics |
| Specialties: |
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| Approaches: | Theoretical, Computational |
The author(s) disclose that the following generative AI tools have been used in the preparation of this submission:
DeepL, Gemini and trinka: English spelling and grammar checkers.
Abstract
Altermagnetism has recently emerged as a third fundamental branch of magnetism, combining the vanishing net magnetization of antiferromagnets with the high-momentum-dependent spin splitting of ferromagnets. This study provides a comprehensive real- and momentum-space analysis of topological phases in two-dimensional d-wave altermagnets. By employing a tight-binding Hamiltonian, we characterize the topological phase transition occurring at a critical intra-sublattice hopping strength ($t_a^C$). We examine the emergence of Dirac nodal points and the resulting Berry curvature singularities, supported by a visual analysis of pseudospin texture winding. Crucially, we analize spin splitting, effective altermagnetic strength, and investigate the transport implications of these phases, uncovering giant conductivity anisotropy and spin-dependent "steering" effects driven by group velocity distribution across the Fermi surface. Beyond bulk properties, we analyze the edge state topology in ribbon geometries through the lens of information-theoretic markers like fidelity-susceptibility and inverse participation ratio, offering an alternative to traditional Chern number calculations. Our results demonstrate that the hybridization of edge states in ultra-narrow nanoribbons opens a controllable energy gap, a feature we exploit to propose a novel topological altermagnetic field-effect transistor design where ballistic and spatially spin-polarized transport can be electrostatically gated. This work establishes a theoretical and information-theoretic framework for "edgetronics" in altermagnetic materials, paving the way for next-generation, high-speed spintronic and "spin-splitter" logic devices and architectures.
Author indications on fulfilling journal expectations
- Provide a novel and synergetic link between different research areas.
- Open a new pathway in an existing or a new research direction, with clear potential for multi-pronged follow-up work
- Detail a groundbreaking theoretical/experimental/computational discovery
- Present a breakthrough on a previously-identified and long-standing research stumbling block
Current status:
Reports on this Submission
Report
In the current work, the author departs from a a model of electronic structure for an altermagnet, calculates the eigenenergies and analyses the structure of the eigenstates. In the following sections, the author calculates and discusses consequences of the properties of the model. Indeed, the author does not specify any material system that the investigation is connected to. However, the model and its properties seem to be quite different from what is discussed in the literature as representative minimal models for altermagnetism. Therefore, I believe it is in place to ask the author to give a few clarification comments on the model, its applicability and connections to models in the literature. This information should allow to referee the rest of the manuscript in view of further comments and judgments about relevance for the scientific literature.
Questions: 1) The model as depicted in Fig. 1 Left and detailed in Eqs. (1-5) is a version of a tight-binding model in presence of exchange fields of the two sublattices. The author has explicitly chosen +t_a for the yellow bonds and -t_a for the green bonds. This choice seems fine-tuned, i.e. in real materials there exists no symmetry that forces the values to be same magnitude, opposite sign. Correct? How do the conclusions of the manuscript change if the two hoppings are tuned away from that value? 2) The author plots the band structure in Fig. 3 Right, but does not show the relevant path that leads to the “Dirac cones” as discussed in section III. Can such a plot be added to allow understanding of the band structure on this important question? 3) At the same time, there is another special choice of J=t, an unexpected choice for a real material where the exchange field is not expected to match the nearest neighbor hopping. Which of the conclusions are robust if going away from this second fine-tuned point in parameter space? 4) The author shows in Fig. 1 (middle) another model dubbed as “d_xy” altermagnet. First, this lattice seems just a rotated version of Fig. 1 (left), i.e. does not describe another physical system and should not be called d_xy altermagnet. (In the known literature about models of altermagnets, there is indeed the possibility of different types of spin splitting; this is however bound to the point group of the underlying lattice.) Second, the indicated “elementary cell” cannot be used to tile the lattice using orthogonal lattice vectors, so the corresponding “Brillouin zone” in Fig. 1 (right) seems not correct. By the way, the area of the elementary cell in Fig. 1 (left) and (middle) is identical, so the “area” of the corresponding Brillouin zones should be identical as well. 5) Minor comment: As the work is not targeted to any material, there is no need to fix the hopping element to 1meV (a value that is too small for real materials anyhow); better use t as natural energy unit. Same for the lattice constant which is arbitrarily set to “1 nm”.
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