  The existence of several 2D materials with heavy atoms in their composition
has been recently demonstrated. The electronic and optical properties of these
materials can be accurately computed with numerically intensive density
functional theory methods. However, it is desirable to have simple effective
models that can accurately describe these properties at low energies. Here we
present an effective model for stanene that is reliable for electronic and
optical properties for photon energies up to 1.1 eV. For this material, we find
that a quadratic model with respect to the lattice momentum is the best suited
for calculations based on the bandstructure, even with respect to band warping.
We also find that splitting the two spin-z subsectors is a good approximation,
which indicates that the lattice buckling can be neglected in calculations
based on the bandstructure. We illustrate the applicability of the model by
computing the linear optical injection rates of carrier and spin densities in
stanene. Our calculations indicate that an incident circularly polarized
optical field only excites electrons with spin that matches its helicity.
