Energy transport in one- and two-dimensional anharmonic lattices with isotopic disorder

Abstract

We present results from computer simulations of anharmonic vibrations of one- and two-dimensional lattices. For disordered systems we have found that anharmonicity destabilizes the localized modes and that, when energy is fed locally to the lattice, it spreads out beyond the localization length via some kind of anomalous diffusion. Moreover, the diffusion exponent \ensuremath{\nu} seems dependent on the strength of anharmonicity but not on the amount of disorder. In perfect lattices we have observed the (-1/2;1;-1/2) localized mode predicted recently [S. Taken, K. Kisoda, and A. J. Sievers, Prog. Theor. Suppl. 94, 242 (1988)].