  We consider states localized by electrostatic potentials in phosphorene using
an atomistic tight binding approach. From the results of the tight-binding
calculations of the confined states we extract effective masses for the
conduction band electrons in the armchair and zigzag directions. The masses
derived in this way are used for a simple single-band effective mass model
which, as we find, reproduces very well the tight-binding energy spectrum in
external magnetic field, the probability densities and the interaction effects.
Both methods produce Wigner crystallization for the ground-state of the
electron pair with the single-electron islands separated in the armchair
direction already for small quantum dots.
