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| Main Authors: | , , , , , , , , , , , |
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| Format: | Preprint |
| Published: |
2026
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| Subjects: | |
| Online Access: | https://arxiv.org/abs/2606.02527 |
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| _version_ | 1866911742370512896 |
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| author | Wei, Chao-Chun Li, Xiaoyin Adams, Sophia Jensen, Jacob Kjeldahl Zhang, Qiang Liu, Jue Avdeev, Maxim Yadav, Dinesh Kumar Deshpande, Vikram V. Whittaker-Brooks, Luisa Liu, Feng Ji, Huiwen |
| author_facet | Wei, Chao-Chun Li, Xiaoyin Adams, Sophia Jensen, Jacob Kjeldahl Zhang, Qiang Liu, Jue Avdeev, Maxim Yadav, Dinesh Kumar Deshpande, Vikram V. Whittaker-Brooks, Luisa Liu, Feng Ji, Huiwen |
| contents | Weyl semimetals and altermagnets represent two distinct classes of quantum materials exhibiting nontrivial topological and magnetic order, respectively. Here we report the realization of a Weyl nodal-loop altermagnet in Cr$_7$Se$_8$, combining neutron diffraction and first-principles calculations. The hexagonal system hosts a coplanar $120^\circ$ compensated magnetic order on a triangular lattice, which breaks inversion-time-reversal and translation-time-reversal symmetries simultaneously while preserving a crystalline mirror plane. The resulting electronic structure features linearly dispersing nodal loops close to the Fermi level ($E_F$) confined to the mirror-invariant $k_z=0$ plane. Along high-symmetry directions, the crossings near $E_F$ form Dirac-like fourfold degeneracies in the absence of spin-orbit coupling; at generic momenta, these crossings split into twofold and form continuous Weyl-like nodal loops protected by mirror symmetry. The momentum-dependent spin polarization exhibits an $f$-wave-like pattern characteristic of odd-parity altermagnets. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2606_02527 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | Symmetry-Protected Weyl Nodal Loops in a Triangular Altermagnet Wei, Chao-Chun Li, Xiaoyin Adams, Sophia Jensen, Jacob Kjeldahl Zhang, Qiang Liu, Jue Avdeev, Maxim Yadav, Dinesh Kumar Deshpande, Vikram V. Whittaker-Brooks, Luisa Liu, Feng Ji, Huiwen Materials Science Weyl semimetals and altermagnets represent two distinct classes of quantum materials exhibiting nontrivial topological and magnetic order, respectively. Here we report the realization of a Weyl nodal-loop altermagnet in Cr$_7$Se$_8$, combining neutron diffraction and first-principles calculations. The hexagonal system hosts a coplanar $120^\circ$ compensated magnetic order on a triangular lattice, which breaks inversion-time-reversal and translation-time-reversal symmetries simultaneously while preserving a crystalline mirror plane. The resulting electronic structure features linearly dispersing nodal loops close to the Fermi level ($E_F$) confined to the mirror-invariant $k_z=0$ plane. Along high-symmetry directions, the crossings near $E_F$ form Dirac-like fourfold degeneracies in the absence of spin-orbit coupling; at generic momenta, these crossings split into twofold and form continuous Weyl-like nodal loops protected by mirror symmetry. The momentum-dependent spin polarization exhibits an $f$-wave-like pattern characteristic of odd-parity altermagnets. |
| title | Symmetry-Protected Weyl Nodal Loops in a Triangular Altermagnet |
| topic | Materials Science |
| url | https://arxiv.org/abs/2606.02527 |