Abstract
We present a systematic analytical study of the soliton excitations in a one-dimensional diatomic lattice with nonlinear on-site potential and a quartic interaction between nearest neighbors. We show that (1) the decoupling ansatz widely used in literature for the motion of two different masses is unncessary and can be naturally derived in our approach; (2) the system may support some new types of gap solitons and resonant kinks, two of which have been observed recently in a nonlinear diatomic pendulum lattice experiment; (3) for nonlinear on-site potential when the wave number of carrier waves is near the edge of the Brillouin zone and the difference of mass between two kinds of atoms becomes small, the results coincide with that of Kivshar and Flytzanis about the gap solitons in diatomic lattices; and (4) the theoretical results, being without any divergence, are valid in the whole Brillouin zone and can be applied to other nonlinear lattices.
Published Version
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