Bethe splitting of exciton bands and solitons

Abstract

The formation of solitons and bisolitons under the conditions of Bethe splitting of exciton bands is analysed by means of an equivalent Hamiltonian, which is correct up to terms linear in the ratio of exciton bandwidth and isolated molecule excitation energy. Several types of solitons appear in such a system and their properties are analysed, as well as the conditions for bisoliton formation and their properties. It is shown that two solitons of the same type can always form a bisoliton, while two solitons of different types can form a bisoliton only under certain conditions related to the ratios of their effective masses and their coupling constants. Special conditions are indicated when the binding energy of two solitons of different type can be higher than the binding energy of two solitons of the same type. These conditions present the basis for the stability analysis of bound soliton states.