  The gap in bilayer graphene (BLG) can directly be controlled by a
perpendicular electric field. By tuning the field through zero at a finite rate
in neutral BLG, excited states are produced. Due to screening, the resulting
dynamics is determined by coupled non-linear Landau-Zener models. The generated
defect density agrees with Kibble-Zurek theory in the presence of subleading
logarithmic corrections. After the quench, population inversion occurs for
wavevectors close to the Dirac point. This could, at least in principle provide
a coherent source of infra-red radiation with tunable spectral properties
(frequency and broadening). Cold atoms with quadratic band crossing exhibit the
same dynamics.
