Excitation spectrum of a two-component Bose-Einstein condensate in a   ring potential
  A mixture of two distinguishable Bose-Einstein condensates confined in a ring potential has numerous interesting properties under rotational and solitary-wave excitation. The lowest-energy states for a fixed angular momentum coincide with a family of solitary-wave solutions. In the limit of weak interactions, exact diagonalization of the many-body Hamiltonian is possible and permits evaluation of the complete excitation spectrum of the system. 
J. Smyrnakis, M. Magiropoulos, A. D. Jackson, G. M. Kavoulakis
cond-mat.quant-gas quant-ph