Instanton in Disordered Peierls Systems

We study disordered Peierls systems described by the Fluctuating Gap Model. We show that the typical electron states with energies lying deep inside the pseudogap are localized near large disorder fluctuations (instantons), which have the form of a soliton-antisoliton pair. Using the ``saddle-point'' method we obtain the average density of states and the average optical absorption coefficient at small energy.