%0 Journal Article %T Tuning of energy levels and optical properties of graphene quantum dots %A Z. Z. Zhang %A Kai Chang %A F. M. Peeters %J Physics %D 2008 %I arXiv %R 10.1103/PhysRevB.77.235411 %X We investigate theoretically the magnetic levels and optical properties of zigzag- and armchair-edged hexagonal graphene quantum dots (GQDs) utilizing the tight-binding method. A new bound edge state at zero energy appears for the zigzag GQDs in the absence of a magnetic field. The magnetic levels of GQDs exhibit a Hofstadter-butterfly spectrum and approach the Landau levels of two-dimensional graphene as the magnetic field increases. The optical properties are tuned by the size, the type of the edge, and the external magnetic field. %U http://arxiv.org/abs/0805.0454v1