  In a nanographene ring with zigzag edges, the spin-polarized state and the
charge-polarized state are stabilized by the on-site and the nearest neighbor
Coulomb repulsions, U and V, respectively, within the extended Hubbard model
under the mean field approximation. In a Moebius strip of the nanographene with
a zigzag edge, U stabilizes two magnetic states, the domain wall state and the
helical state. Both states have ferrimagnetic spins localized along the zigzag
edge while the former connects the opposite ferrimagnetic orders resulting in a
magnetic frustration forced by the topology and the latter rotates the
ferrimagnetic spins uniformly to circumvent the frustration. The helical state
is lower in energy than the domain wall state. On the other hand, V stabilizes
another domain wall state connecting the opposite charge orders.
