The two-dimensional Dirac Hamiltonian with equal scalar and vector potentials
has been proved commuting with the deformed orbital angular momentum L. When
the potential takes the Coulomb form, the system has an SO(3) symmetry, and
similarly the harmonic oscillator potential possesses an SU(2) symmetry. The
generators of the symmetric groups are derived for these two systems
separately. The corresponding energy spectra are yielded naturally from the
Casimir operators. Their non-relativistic limits are also discussed.Comment: 3 pages, Accepted by Annals of Physics (New York