Discovery of 2D Anisotropic Dirac Cones

Abstract

2D anisotropic Dirac cones are observed in χ₃ borophene, a monolayer boron sheet, using high-resolution angle-resolved photoemission spectroscopy. The Dirac cones are centered at the X and X′ points. The data also reveal that the hybridization between borophene and Ag(111) is very weak, which explains the preservation of the Dirac cones. As χ₃ borophene has been predicated to be a superconductor, the results may stimulate further research interest in the novel physics of borophene, such as the interplay between Cooper pairs and the massless Dirac fermions.

χ₃ borophene hosts highly anisotropic Dirac cones with triangular pyramid shape. Along the specific direction, the Fermi velocity is as large as that of graphene. The first-principles calculations reproduce the experimental bands and reveal a weak electronic hybridization between the borophene and the substrate. These results highlight the promising application of borophene in novel quantum devices.

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