Quantum internal modes of solitons in a one-dimensional easy-plane antiferromagnet in a strong magnetic field

We use the effective Lagrangian approach to study the dynamics of solitons in a one-dimensional easy-plane Heisenbeg antiferromagnet in the presence of a strong external in-plane magnetic field H close to a certain critical value H-c similar or equal to(HeHa)(1/2) (where H-e and H-a are the exchange and anisotropy fields, respectively). We show that the dynamics of internal soliton degrees of freedom is essentially quantum, and they are strongly coupled to the ''translational'' mode of soliton movement. These peculiarities lead to considerable changes in the response functions of the system that can be detected experimentally; we discuss the possibility to observe the signatures of internal soliton modes in (CD3)(4)NMnCl3 (TMMC).