  In the teleparallel framework of cosmology, a quintessence with non-minimal
couplings to the scalar torsion and a boundary term is considered. A conformal
coupling to matter density is also taken into account. It is shown that the
model can describe the onset of cosmic acceleration after an epoch of matter
dominated era, where dark energy is negligible, via $Z_2$ symmetry breaking.
While the conformal coupling holds the Universe in a state with zero dark
energy density in the early epoch, the non-minimal couplings lead the Universe
to a stable state with de Sitter expansion at the late time.
