  In addition to mechanisms already proposed to account for the formation in
manganites of a small-polaron superlattice above the Curie temperature Tc and
to a metallic-like sea of large polarons below Tc, we now consider other
observed colossal-resistance inducing fields, such as magnetic, electric,
photon, or strain fields. We attribute the charge-ordered phase formation to
the occurrence of strong dipolar binding of vibronic small polarons arising
from the phonon coupling of highly polarizable two-level orbital systems. These
species having associated inherent electric and magnetic off-center dipoles,
they couple to the external fields leading to the observed colossal effects.
The random phase appears due to polaron band widening in the external field.
