Is a conjugated polymer a Mott or a Peierls insulator?

Abstract

By considering the full repulsion between electrons, it is found that the interaction range is a decisive factor to determine the effect of the electron interaction on the optical gap of the conjugated polymers. If the range is long, the gap is mainly produced by the electron interaction and the polymer is Mott insulator. But, if the range is short, the optical gap is suppressed by the electron interaction, then it is Peierls insulator. © 1991.