Atomic collapse in graphene

Since the discovery that electrons in graphene behave as massless Dirac fermions the single atom thick material has become a fertile playground for testing exotic predictions of quantum electrodynamics such as Klein tunneling and the fractional quantum Hall effect Now add to that list atomic collapse the spontaneous formation of electrons and positrons in the electrostatic field of a superheavy atomic nucleus The atomic collapse was predicted to manifest itself in quasistationary states which have complex valued energies and which decay rapidly However the atoms created