  We investigate the role of electron-electron interaction in a two-band
Hubbard model based on the Bernevig-Hughes-Zhang Hamiltonian exhibiting the
quantum spin Hall (QSH) effect. By means of dynamical mean-field theory, we
find that a system with topologically trivial non-interacting parameters can be
driven into a QSH phase at finite interaction strength by virtue of local
dynamical fluctuations. For very strong interaction, the system reenters a
trivial insulating phase by going through a Mott transition. We obtain the
phase diagram of our model by direct calculation of the bulk topological
invariant of the interacting system in terms of its single particle Green's
function.
