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arXiv · 1901.08413

Hexagonal supertetrahedral boron: A topological metal with multiple spin-orbit-free emergent fermions

Yan Gao·Weikang Wu·Peng-Jie Guo·Chengyong Zhong·Shengyuan A. Yang·Kai Liu·Zhong-Yi Lu
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Abstract

We predict a new three-dimensional (3D) boron allotrope based on systematic first-principles electronic structure calculations. This allotrope can be derived by substituting each carbon atom in a hexagonal diamond lattice with a B$_{4}$ tetrahedron and possesses the same space group $P6_{3}/mmc$ as hexagonal diamond, hence it is termed as H-boron. We show that H-boron has good stability and excellent mechanical property. Remarkably, we find that H-boron is a topological metal with rich types of spin-orbit-free emergent fermions, including semi-Dirac fermion, quadratic and linear triple-point fermion, nodal-line fermion, and nodal-surface fermion. We clarify their symmetry protections and characterize them by constructing the corresponding low-energy effective models. Our work not only discovers a new boron allotrope with excellent properties, it also offers a platform to explore interesting physics of new kinds of emergent fermions.

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Yan Gao, Weikang Wu, Peng-Jie Guo, Chengyong Zhong, Shengyuan A. Yang, Kai Liu, Zhong-Yi Lu. 2019-01-24. Hexagonal supertetrahedral boron: A topological metal with multiple spin-orbit-free emergent fermions. https://doi.org/10.1103/physrevmaterials.3.044202

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