A New Anisotropic Dirac Cone Material: A B2S Honeycomb Monolayer.

Different from the isotropic Dirac cones existing in other two-dimensional (2D) materials, anisotropic Dirac cones have the merit of anisotropic carrier mobility for applications in direction-dependent quantum devices. Motivated by the recent experimental finding of an anisotropic Dirac cone in borophene, here we report a new 2D anisotropic Dirac cone material, B2S monolayer, identified by using a global structure search method and first-principles calculation combined with a tight-binding model. The B2S monolayer is found to be stable mechanically, thermally, and dynamically and exhibits an anisotropic Dirac cone exactly at the Fermi level, showing a Fermi velocity of 106 m/s in the same order of magnitude as that of graphene. Moreover, B2S monolayer is the first anisotropy Dirac cone material with a pristine honeycomb structure stabilized by S in free-standing conditions where each atom has four valence electrons on average being isoelectronic to C. This study would expand the Dirac cone material family with new features.