The coexistence of Brownian and non-Gaussian diffusion dynamics within a wide array of physical and biological systems has been a subject of considerable interest and investigation, traditionally through direct space observations.
In this talk, I will report a novel methodology employing reciprocal space analysis to probe Brownian yet non-Gaussian (BNG) diffusion in a glassy material. Our approach, based on Differential Dynamic Microscopy (DDM), allows for the analysis of density fluctuations induced by particle motion across different wave vectors, offering a complementary viewpoint to the conventional particle tracking techniques.
I will discuss experiments performed on small diluted tracers diffusing in a dense matrix of larger colloidal hard spheres with volume fractions above the glass transition. We focus on conditions known as the “single-glass” state, where small particles behave like diluted tracers exploring a complex, heterogeneous, albeit dynamically quasi-arrested environment.
Our experimental results, mapped against predictions of the diffusing diffusivity model, reveal the utility of reciprocal space analysis in deciphering the underlying mechanisms of BNG diffusion, particularly in contexts where direct observation of individual particle trajectories is challenged by the physical constraints of the system.
Our findings offer a robust framework for investigating the fast, anomalous dynamics characteristic of crowded environments—a scenario prevalent in many material and biological contexts, emphasizing the role of reciprocal space analysis in the exploration of complex diffusive behaviors.