  An interesting property of zigzag graphene nanoribbons is the presence of
edge states which are extended along its borders but localized in the
transverse direction. We show that because of this property, electron transport
through an externally induced potential well displays two-paths-interference
oscillations when subject either to a magnetic or a transverse electric field.
This effect does not require the existence of an actual `hole' in the
nanoribbon's geometry. Moreover, since edge states are spin polarized, having
opposite polarization on opposite sides, such interference effect can be used
to rotate the spin of the incident carriers in a controlled way.
