  We report quantum interference effects in the electrical conductance of
chemical vapor deposited graphene nanoconstrictions fabricated using feedback
controlled electroburning. The observed multimode Fabry-Perot interferences can
be attributed to reflections at potential steps inside the channel. Sharp
antiresonance features with a Fano line shape are observed. Theoretical
modeling reveals that these Fano resonances are due to localized states inside
the constriction, which couple to the delocalized states that also give rise to
the Fabry-Perot interference patterns. This study provides new insight into the
interplay between two fundamental forms of quantum interference in graphene
nanoconstrictions.
