First-principles calculations of a robust two-dimensional boron honeycomb sandwiching a triangular molybdenum layer

A graphenelike two-dimensional boron honeycomb is inherently prohibited due to its empty {π} valence band. Based on chemical intuition and first-principles calculations, we design a two-dimensional crystal MoB₄ with two graphenelike boron honeycombs sandwiching a triangular molybdenum layer. It has the attractive electronic structure of double Dirac cones near Fermi level with high Fermi velocity, which are contributed by the coupling of Mo d orbitals and B pz orbitals. Such a metal stabilized boron honeycomb system could even have both superconductivity and ferromagnetism through appropriate selection of the metal layer, such as manganese. The unique electronic properties of these two-dimensional systems inspire broad interest in nanoelectronics.