  Recently phosphorene, monolayer honeycomb structure of black phosphorus, was
experimentally manufactured and attracts rapidly growing interests. Here we
investigate stability and electronic properties of honeycomb structure of
arsenic system based on first principle calculations. Two types of honeycomb
structures, buckled and puckered, are found to be stable. We call them arsenene
as in the case of phosphorene. We find that both the buckled and puckered
arsenene possess indirect gaps. We show that the band gap of the puckered and
buckled arsenene can be tuned by applying strain. The gap closing occurs at 6%
strain for puckered arsenene, where the bond angles between the nearest
neighbour become nearly equal. An indirect-to-direct gap transition occurs by
applying strain. Especially, 1% strain is enough to transform the puckered
arsenene into a direct-gap semiconductor. Our results will pave a way for
applications to light-emitting diodes and solar cells.
