Electronic-mechanical coupling in 2D dirac materials

Full text: The discovery and exploration of graphene has stimulated intensive research in recent years, leading to the identification and study of a wide range of two-dimensional (2D) materials that exhibit a rich variety of novel structural, electronic, catalytic, and mechanical properties. We report findings of an extraordinary combination of unusual mechanical and electronic properties in hydrogenated borophene, known as borophane, from first-principles calculations. This novel 2D material has been shown to exhibit robust Dirac transport physics. Our study unveils that borophane is auxetic with a surprising negative Poisson's ratio stemming from its unique puckered triangle hinge structure and the associated hinge dihedral angle variation under a tensile strain in the armchair direction. Our results also identify borophane to be ferroelastic with a stress-driven 90-degree lattice rotation in the boron layer, accompanied by a remarkable orientation switch of the anisotropic Dirac transport channels. On the other hands, 2D topological insulators possess the helical metallic edge states, which exhibit interesting Dirac cone feature. We have demonstrated several feasible approaches to turn the graphene into strong topological insulators. (author)