Higher-order Weyl nodes driven by helical magnetic order in EuAgAs
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arXiv
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| Main Authors: | , , , , , , , , , , |
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| Format: | Preprint |
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2026
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| _version_ | 1866910235014201344 |
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| author | Soh, Jian-Rui Zhu, Ziming Withers, Louis Rodríguez-Velamazán, J. Alberto Kim, Timur K. Fabelo, Oscar Stunault, Anne Yevtushynsky, Daniil Prabhakaran, Dharmalingam Yang, Shengyuan A. Boothroyd, Andrew T. |
| author_facet | Soh, Jian-Rui Zhu, Ziming Withers, Louis Rodríguez-Velamazán, J. Alberto Kim, Timur K. Fabelo, Oscar Stunault, Anne Yevtushynsky, Daniil Prabhakaran, Dharmalingam Yang, Shengyuan A. Boothroyd, Andrew T. |
| contents | Magnetic topological semimetals provide a fertile ground for exploring how long-range magnetic order can alter electronic band structures and generate novel quasiparticles such as Weyl fermions. Here, we investigate the coupled magnetic and electronic structure of single-crystalline EuAgAs, a hexagonal pnictide whose magnetic ground state has remained elusive. Using neutron diffraction and resonant elastic X-ray scattering, we identify an unusual magnetic ordering sequence with two successive phase transitions at $T_\mathrm{N1} = 12$ K and $T_\mathrm{N2} = 8$ K. We observe two slightly different magnetic propagation vectors, one associated with $T_\mathrm{N1}$ and the other with $T_\mathrm{N2}$. Spherical neutron polarimetry reveals that the magnetic structure is a transverse helix aligned along the $c$ axis with a period that is approximately twice the $c$ lattice parameter. First-principles calculations for the helical phase predict subtle band folding effects and the emergence of effective higher-order Weyl nodes. These topological features appear near the calculated Fermi energy $E_{\mathrm{F}}$ which, however, lies above the position of $E_{\mathrm{F}}$ obtained from angle-resolved photoemission spectroscopy so could not be probed in this study. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2605_19347 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | Higher-order Weyl nodes driven by helical magnetic order in EuAgAs Soh, Jian-Rui Zhu, Ziming Withers, Louis Rodríguez-Velamazán, J. Alberto Kim, Timur K. Fabelo, Oscar Stunault, Anne Yevtushynsky, Daniil Prabhakaran, Dharmalingam Yang, Shengyuan A. Boothroyd, Andrew T. Strongly Correlated Electrons Magnetic topological semimetals provide a fertile ground for exploring how long-range magnetic order can alter electronic band structures and generate novel quasiparticles such as Weyl fermions. Here, we investigate the coupled magnetic and electronic structure of single-crystalline EuAgAs, a hexagonal pnictide whose magnetic ground state has remained elusive. Using neutron diffraction and resonant elastic X-ray scattering, we identify an unusual magnetic ordering sequence with two successive phase transitions at $T_\mathrm{N1} = 12$ K and $T_\mathrm{N2} = 8$ K. We observe two slightly different magnetic propagation vectors, one associated with $T_\mathrm{N1}$ and the other with $T_\mathrm{N2}$. Spherical neutron polarimetry reveals that the magnetic structure is a transverse helix aligned along the $c$ axis with a period that is approximately twice the $c$ lattice parameter. First-principles calculations for the helical phase predict subtle band folding effects and the emergence of effective higher-order Weyl nodes. These topological features appear near the calculated Fermi energy $E_{\mathrm{F}}$ which, however, lies above the position of $E_{\mathrm{F}}$ obtained from angle-resolved photoemission spectroscopy so could not be probed in this study. |
| title | Higher-order Weyl nodes driven by helical magnetic order in EuAgAs |
| topic | Strongly Correlated Electrons |
| url | https://arxiv.org/abs/2605.19347 |