Mode-conversion effects of phonons on Anderson localization

Numerically investigating mode-conversion effects of phonons on Anderson localization in random superlattices, we make it clear the changes in localization properties when the LA and TA phonons which independently show Anderson localization for the normal incidence interact as the incident angles increase. The mode conversions which occur for oblique propagation at small incident angles induce collaboration among the phonons, giving rise to extension of the localization length or delocalization, depending on the system size. On the other hand, at large incident angles, the transmission decay becomes larger than for the normal incidence. In contrast to the small incident angles, the transmission decay and transmission fluctuations become independent of the incident phonon modes and show the frequency dependences that are not predictable from those at the small incident angles, evidencing that the coupled modes of phonons are formed by the mode conversions.