Localization in one-dimensional chains with L\'evy-type disorder

We study Anderson localization of the classical lattice waves in a chain with mass impurities distributed randomly through a power-law relation $s^{-(1+\alpha)}$ with $s$ as the distance between two successive impurities and $\alpha>0$. This model of disorder is long-range correlated and is inspired by the peculiar structure of the complex optical systems known as L\'evy glasses. Using theoretical arguments and numerics, we show that in the regime in which the average distance between impurities is finite with infinite variance, the small-frequency behaviour of the localization length is $\xi_\alpha(\omega) \sim \omega^{-\alpha}$. The physical interpretation of this result is that, for small frequencies and long wavelengths, the waves feel an effective disorder whose fluctuations are scale-dependent. Numerical simulations show that an initially localized wavepacket attains, at large times, a characteristic inverse power-law front with an $\alpha$-dependent exponent which can be estimated analytically.