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Cat's-cradle-like Dirac semimetals in layer groups with multiple screw axes: Application to two-dimensional borophene and borophane

2018; American Physical Society; Volume: 98; Issue: 19 Linguagem: Inglês

10.1103/physrevb.98.195437

2469-9977

Xiaotong Fan, Da‐Shuai Ma, Botao Fu, Cheng‐Cheng Liu, Yugui Yao,

2D Materials and Applications

Recently, the crystal symmetry-protected topological semimetals have aroused extensive interest, especially the nonsymmorphic symmetry-protected one. We list the possible nonmagnetic topological semimetals and develop their $k\ifmmode\cdot\else\textperiodcentered\fi{}p$ Hamiltonian in all layer groups with multiple screw axes in the absence of spin-orbital coupling. We find a cat's-cradle-like topological semimetal phase which looks like multiple hourglasslike band structures staggered together. Furthermore, we propose monolayer borophene and borophane with the $pmmn$ layer group as the first material class to realize such a semimetal phase. A pair of tilted anisotropic Dirac cones at the Fermi level is revealed in two-dimensional boron-based materials, and the low-energy effective models are given. Moreover, akin to a three-dimensional Weyl semimetal, the topological property of these cat's-cradle-like Dirac semimetals can be verified by the calculation of a quantized Berry phase and the demonstration of a flat Fermi-arc edge state connecting two Dirac points as well. Our finding that borophene and borophane are cat's-cradle-like Dirac semimetals is of great interest for experiment and possible applications in the future.