Low-temperature electron states at a Peierls instability of order-disorder type

A one-dimensional system with electronic Peierls instability of order-disorder type is investigated in the tight-binding approximation in the case of a half-filled band. The corresponding critical temperature is estimated in the self-consistent field approximation. An exact solution is obtained for the electron states in the presence of a domain wall at low temperatures; it is used to calculate the energy of the domain wall and predict the appearance of additional states at the center of the Peierls gap and outside the regular electron spectrum. The rearrangement of the electron spectrum with the appearance of additional states when pairs of domain walls are created is also discussed.