Shallow energy levels around solitons, polarons and bipolarons in quasi-one-dimensional MX compounds

Shallow energy levels in quasi-one-dimensional MX compounds have been found firstly by considering the two-band tight-binding model. These shallow levels are situated at the band edges of the CB and VB. The electronic states of the shallow levels are localized around solitons, polarons and bipolarons. It is expected that these shallow levels could be observed in the absorption spectrum of MX compounds. Finally, the effect of e-e interactions on the shallow levels was studied, it has been found that e-e interactions will decrease the mini-gap between the shallow levels and CB and increase the mini-gap between the shallow levels and VB.