Disorder Induced Anomalous Mobility Enhancement in Confined Geometries

Strong trapping events leading to a significant slowdown of transport, compared to regular Brownian motion and termed anomalous, have been observed in a growing number of systems, such as amorphous materials, living cells, and rheological environments. Such trapping events are typically treated as uncorrelated, implying some level of homogeneity in the system which is not always true. Our findings suggest that correlated disorder, i.e. quenched, can reshape our understanding of transport problems in narrow channels when anomalous transport is in play. Specifically, in a two-dimensional channel with width w, under external drive, tighter geometrical constraints (smaller w) enhance mobility. Such behavior is not expected based on regular or even anomalous transport dynamics and is rooted in the statistics of rare events, notably extremely large trapping times, resulting in surprising alterations to motion dynamics. We derive an explicit form of the response to an external force, as well as the time-averaged single trajectory displacement, by utilizing the double-subordination approach for the quenched trap model. A technique to identify quenched disorder in a system from experimental time series data is suggested.