  We show that surface plasmons of a two-dimensional Dirac metal such as
graphene can be reflected by line-like perturbations hosting one-dimensional
electron states. The reflection originates from a strong enhancement of the
local optical conductivity caused by optical transitions involving these bound
states. We propose that the bound states can be systematically created,
controlled, and liquidated by an ultranarrow electrostatic gate. Using infrared
nanoimaging, we obtain experimental evidence for the locally enhanced
conductivity of graphene induced by a carbon nanotube gate, which supports this
theoretical concept.
