Phase-nonlinearity interplay in small quantum systems

We report effects of the interplay of quantum phases and nonlinearity in small quantum systems that are characterized by strong interactions between a quasiparticle (an excitation or an electron) and lattice vibrations, and are described by the discrete nonlinear Schrodinger equation. The issue under investigation is the influence that features of the initial placement of a quasiparticle can have on the process of self-trapping. We find that initial phases profoundly control the dependence of self-trapping on initial inhomogeneity. We also find that the only non-trivial stationary state of the system disappears in the presence of complex initial site amplitudes and that the amplitude of oscillations, which dips sharply to zero at the stationary state for real initial amplitudes, approaches a nonzero minimum for complex initial amplitudes. (C) 1997 Published by Elsevier Science B.V.