Delocalization in harmonic chains with long-range correlated random masses

الأصل · EN

We study the nature of collective excitations in harmonic chains with masses exhibiting long-range correlated disorder with power spectrum proportional to 1/kα, where k is the wave-vector of the modulations on the random masses landscape. Using a transfer matrix method and exact diagonalization, we compute the localization length and participation ratio of eigenmodes within the band of allowed energies. We find extended vibrational modes in the low-energy region for α> 1. In order to study the time evolution of an initially localized energy input, we calculate the second moment M₂(t) of the energy spatial distribution. We show that M₂(t), besides being dependent of the specific initial excitation and exhibiting an anomalous diffusion for weakly correlated disorder, assumes a ballistic spread in the regime α>1 due to the presence of extended vibrational modes.