  In this contribution, we propose a new model for studying the confinement of
a spin-half particle to a two-dimensional quantum ring in systems described by
the Dirac equation by introducing a new minimal coupling into the Dirac
equation. We show that the introduction of this new minimal coupling into the
Dirac equation yields a generalization of the two-dimensional model for a
quantum ring proposed by Tan and Inkson [W.-C. Tan and J. C. Inkson, Semicond.
Sci. Technol. {\bf11}, 1635 (1996)] for relativistic spin-half quantum
particles.
