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Coexistence of d-wave altermagnetism and topological states in Janus FeSeX (X = S, Te) monolayers

Alvaro González-García1,*, William López-Pérez1, Paola Pacheco2, Luz Ramírez-Montes3, and Rafael González-Hernández1

  • 1Departamento de Física y Geociencias, Universidad del Norte, Km. 5 Vía Antigua Puerto Colombia, Barranquilla 081007, Colombia
  • 2Grupo de Espectroscopia Optica de Emision y Laser, GEOEL, Universidad del Atlantico, Puerto Colombia, Barranquilla 081007, Colombia
  • 3Departamento de Física, Universidad de Sucre, Barrio Puerta Roja, Sincelejo 700001, Colombia

  • *Contact author: alvarogonzalez@uninorte.edu.co
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Phys. Rev. Materials 10, 044004 – Published 28 April, 2026

DOI: https://doi.org/10.1103/3kkj-s5jk

Abstract

The interplay between unconventional magnetism and band topology in two-dimensional materials has emerged as an important theme in condensed matter physics. Here, we present first-principles calculations that reveal the coexistence of d-wave altermagnetism and topological behavior in Janus FeSeX (X = S, Te) monolayers. The chemical asymmetry of the Janus structure breaks both out-of-plane mirror and inversion symmetries, leading to anisotropic exchange interactions and momentum-dependent spin splittings even in the absence of spin-orbit coupling, the defining signature of altermagnetism. Phonon dispersion analyses confirm the dynamical stability of both compounds, while strain-dependent calculations demonstrate that the magnitude of the altermagnetic exchange splitting (Δs) can be efficiently tuned by biaxial strain. When spin-orbit coupling is included, a finite topological band gap emerges at the Fermi level, accompanied by quantized spin Hall conductivity plateaus and nontrivial topological invariants (spin Chern number = 1, Z2=1). These findings establish FeSeS and FeSeTe as promising two-dimensional platforms for realizing topological altermagnetism and spin-orbit-driven charge-spin conversion, thus opening new avenues for low-dissipation spintronic devices.

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This article appears in the following collection:

Altermagnetic and Related Materials

Editors of Physical Review Materials are pleased to present the Collection on Altermagnetic and Related Materials, highlighting cutting-edge advances in theoretical and experimental identification of novel altermagnetic materials, their properties, and their potential applications. The Collection is being guest-edited by Kirill Belashchenko of the University of Nebraska-Lincoln (USA), Cheng Song of Tsinghua University (China), and Peter Wadley of The University of Nottingham (UK). Every article published in this collection underwent a rigorous peer review process, adhering to the same high standards applied to all papers. The Physical Review Materials editorial team managed the peer review and made all editorial decisions.

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Phys. Rev. Materials 10, 044004– Published 28 April, 2026
  • Received 21 November 2025
  • Accepted 12 March 2026
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