  A planar quantum-well device made of a gapless graphene nanoribbon with edges
in contact with gapped graphene sheets is examined. The size-quantization
spectrum of charge carriers in an asymmetric quantum well is shown to exhibit a
pseudospin splitting. Interface states of a new type arise from the crossing of
dispersion curves of gapless and gapped graphene materials. The exciton
spectrum is calculated for a planar graphene quantum well. The effect of an
external electric field on the exciton spectrum is analyzed.
