Delocalization Of Phonons And Energy Spectrum In Disordered Nonlinear Systems

We study phonon delocalization in disordered media in the presence of nonlinearity. By considering the Fermi-Pasta-Ulam beta-model, we show that regardless of whether the initial state of the linear system is localized or not, the final state will be an extended mode after turning on the nonlinear term. We report on the results of an extensive dynamical simulation of a disordered nonlinear system, which show that, independent of the initial mode frequency, in the final state the energy spectrum is excited according to the Kolmogorov spectrum E(omega) similar to omega(-5/3). Finally, we show that disorder will not cause delocalization of intrinsic localized modes.