(A) Electron spectrum E(p) in bilayer graphene (left) and energy dependence of its density of states, DoS (right). At energy levels corresponding to the edge of the "Mexican hat" the DoS tends to infinity.
(B) The red areas show the states of electrons that participate in tunneling in bilayer graphene (left) and in a conventional semiconductor with "ordinary" parabolic bands (right). Electrons that are capable of tunneling at low voltages are found in the ring in graphene, but in the semiconductor they are only found at the single point. The dotted lines indicate the tunneling transitions. The red lines indicate the trajectories of the tunneling electrons in the valence band.