  Among the large number of promising two-dimensional (2D) atomic layer
crystals, true metallic layers are rare. Through combined theoretical and
experimental approaches, we report on the stability and successful exfoliation
of atomically thin gallenene sheets, having two distinct atomic arrangements
along crystallographic twin directions of the parent alpha-gallium. Utilizing
the weak interface between solid and molten phases of gallium, a solid-melt
interface exfoliation technique is developed to extract these layers. Phonon
dispersion calculations show that gallenene can be stabilized with bulk gallium
lattice parameters. The electronic band structure of gallenene shows a
combination of partially filled Dirac cone and the non-linear dispersive band
near Fermi level suggesting that gallenene should behave as a metallic layer.
Furthermore it is observed that strong interaction of gallenene with other 2D
semiconductors induces semiconducting to metallic phase transitions in the
latter paving the way for using gallenene as interesting metallic contacts in
2D devices.
