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| Format: | Preprint |
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2025
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| Accès en ligne: | https://arxiv.org/abs/2510.18426 |
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| _version_ | 1866914105190776832 |
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| author | Gao, Xiao-jing Ge, Yanfeng Gao, Yan |
| author_facet | Gao, Xiao-jing Ge, Yanfeng Gao, Yan |
| contents | Nodal-sphere semimetals (NSSMs), featuring spherical band degeneracies in momentum space, constitute a fascinating class of topological materials. However, their realization in real materials is severely hampered by discrete crystallographic symmetry constraints, often resulting in gapped ``pseudo'' nodal spheres. Here, combining first-principles calculations and symmetry analysis, we predict a new three-dimensional boron allotrope, CT-B$_{24}$, as a nearly ideal NSSM. Its structural stability is systematically confirmed by phonon calculations, \textit{ab initio} molecular dynamics simulations at 600~K, and elastic constant analysis. Notably, the electronic structure of CT-B$_{24}$ exhibits two bands crossing linearly near the Fermi level, forming a quasi-nodal sphere around the $Γ$ point. The maximum energy gap is merely 0.008~meV, which is two orders of magnitude smaller than the gaps reported in previous pseudo-NSSMs. Furthermore, the (001) surface hosts pronounced drumhead-like surface states located outside the projected nodal sphere, providing distinct signatures detectable by angle-resolved photoemission spectroscopy (ARPES). The nodal sphere also demonstrates remarkable robustness and tunability under external strain, driving a topological phase transition from an NSSM to a Dirac semimetal and finally to a trivial insulator. Our work not only presents a superior material platform for exploring nodal-sphere physics but also suggests potential for strain-tunable topological devices. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2510_18426 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Ideal Nodal-Sphere Semimetal in the Three-Dimensional Boron Allotrope CT-B$_{24}$ Gao, Xiao-jing Ge, Yanfeng Gao, Yan Materials Science Nodal-sphere semimetals (NSSMs), featuring spherical band degeneracies in momentum space, constitute a fascinating class of topological materials. However, their realization in real materials is severely hampered by discrete crystallographic symmetry constraints, often resulting in gapped ``pseudo'' nodal spheres. Here, combining first-principles calculations and symmetry analysis, we predict a new three-dimensional boron allotrope, CT-B$_{24}$, as a nearly ideal NSSM. Its structural stability is systematically confirmed by phonon calculations, \textit{ab initio} molecular dynamics simulations at 600~K, and elastic constant analysis. Notably, the electronic structure of CT-B$_{24}$ exhibits two bands crossing linearly near the Fermi level, forming a quasi-nodal sphere around the $Γ$ point. The maximum energy gap is merely 0.008~meV, which is two orders of magnitude smaller than the gaps reported in previous pseudo-NSSMs. Furthermore, the (001) surface hosts pronounced drumhead-like surface states located outside the projected nodal sphere, providing distinct signatures detectable by angle-resolved photoemission spectroscopy (ARPES). The nodal sphere also demonstrates remarkable robustness and tunability under external strain, driving a topological phase transition from an NSSM to a Dirac semimetal and finally to a trivial insulator. Our work not only presents a superior material platform for exploring nodal-sphere physics but also suggests potential for strain-tunable topological devices. |
| title | Ideal Nodal-Sphere Semimetal in the Three-Dimensional Boron Allotrope CT-B$_{24}$ |
| topic | Materials Science |
| url | https://arxiv.org/abs/2510.18426 |