Breakdown of Diffusion in Dynamics of Extended Waves in Mesoscopic Media

TL;DR

This paper observes the breakdown of the diffusion model in mesoscopic media by studying nonexponential decay in microwave transmission, revealing a nearly Gaussian distribution of mode coupling strengths and their scaling with sample length.

Contribution

It provides experimental evidence of diffusion breakdown in extended waves within mesoscopic media and characterizes the mode coupling distribution and its scaling behavior.

Findings

Decay rate of transmission decreases nearly linearly with time

Distribution of mode coupling strengths is nearly Gaussian

Scaling of distribution peak and width with sample length

Abstract

We report the observation of nonexponential decay of pulsed microwave transmission through quasi-one-dimensional random dielectric media that signals the breakdown of the diffusion model of transport for temporally coherent extended waves. The decay rate of transmission falls nearly linearly in time due to a nearly gaussian distribution of the coupling strengths of quasi-normal electromagnetic modes to free space at the sample surfaces. The peak and width of this distribution scale as L^{-2.05} and L^{-1.81}, respectively.