2015/10/10 by Yang Wang, Dillon Wong, Andrey V. Shytov +10 · 2 citations
Physics and Astronomy · #cond-mat.mes-hall
paper · pdf · doi:10.1126/science.1234320
published as Science 340, 734-737 (2013) · 3 figures
arxiv created 2015/10/10 · arxiv updated 2015/10/13
Relativistic quantum mechanics predicts that when the charge of a superheavy atomic nucleus surpasses a certain threshold, the resulting strong Coulomb field causes an unusual atomic collapse state; this state exhibits an electron wave function component that falls toward the nucleus, as well as a positron component that escapes to infinity. In graphene, where charge carriers behave as massless relativistic particles, it has been predicted that highly charged impurities should exhibit resonances corresponding to these atomic collapse states. We have observed the formation of such resonances around artificial nuclei (clusters of charged calcium dimers) fabricated on gated graphene devices via atomic manipulation with a scanning tunneling microscope. The energy and spatial dependence of the atomic collapse state measured with scanning tunneling microscopy revealed unexpected behavior when occupied by electrons.