Negative-donor centers in two dimensions

A variational calculation of the bound states of negative-donor centers ${\mathit{D}}^{\mathrm{-}}$ in two dimensions is presented; exchange and correlation effects are included using a Chandrasekhar-type trial wave function. At zero magnetic field, a binding energy of 0.45 ${\mathrm{Ry}}^{\mathrm{*}}$ is obtained for the singlet ground state, eight times larger than the corresponding value in three dimensions. At very small, but finite magnetic fields, a second (triplet) state becomes bounded.