▎ 摘　　要

We propose to con. ne massless Dirac fermions in a graphene-based quantum annulus induced by an inhomogeneous magnetic field. It is found that influenced by an effective magnetic potential well the degeneracies of the relativistic Landau levels can be lifted, and the angular-momentum transitions in the ground state can occur by adjusting the geometry of the annulus and/or the magnitude of the magnetic field. Especially for high magnetic fields the system can form the strongly localized states in the annulus and around its boundaries, and some energy levels can reconverge to the Landau levels. Moreover, it is predicted that the dipole-allowed optical transitions between the low-lying energy levels can be measured by far-infrared spectroscopy, and the optical spectrum consists of a series of unequally spaced peaks. Copyright (C) EPLA, 2009