  The bulk conductivity of a two-dimensional system is studied assuming that
quantum interference effects break time-reversal symmetry in the presence of
strong spin-orbit interaction and strong lattice potential. The study is
carried out by direct diagonalization in order to explore the
nonlinear-response regime. The system displays a quantized conductivity that
depends on the intensity of the electric field and under specific conditions
the conductivity limit at zero electric field shows a nonvanishing value.
