Quantum breathers in a nonlinear Klein Gordon lattice

The quantum modes of a nonlinear Klein Gordon lattice have been computed numerically [L. Proville, Phys. Rev. B 71 (2005) 104306]. The on-site nonlinearity has been found to lead to a phonon pairing and consequently some phonon bound states. In the present paper, the time-dependent Wannier transform of these states is shown to exhibit a breather-like behavior, i.e., it is spatially localized and time-periodic. The typical time the lattice may sustain such breather states is studied as a function of the trapped energy and the intersite lattice coupling.