  Defect formation in the one-dimensional topological three-band model is
examined within both lattice and continuum models. Classic results of
Jackiw-Rebbi and Rice-Mele for the soliton charge is generalized to the
three-band model. The presence of the central flat band in the three-band model
makes the soliton charge as a function of energy behave in a qualitatively
different way from the two-band Dirac model case. Quantum field-theoretical
calculation of Goldstone and Wilczek is also generalized to the three-band
model to obtain the soliton charge. Diamond-chain lattice is shown to be an
ideal structure to host a topological three-band structure.
