Department of Chemical, Materials and Production Engineering, University of Naples Federico II, P.le Tecchio 80, Napoli 80125, Italy.
Department of Physics E. Pancini, University of Naples Federico II, Complesso Universitario Monte S. Angelo, Via Cintia, I-80126 Naples, Italy.
Phys Rev Lett. 2021 Apr 16;126(15):158003. doi: 10.1103/PhysRevLett.126.158003.
The recently discovered Fickian yet non-Gaussian diffusion (FnGD) is here finely tuned and investigated over a wide range of probabilities and timescales using a quasi-2D suspension of colloidal beads under the action of a static and spatially random optical force field. This experimental model allows one to demonstrate that a "rapid" FnGD regime with a diffusivity close to that of free suspension can originate from earlier subdiffusion. We show that these two regimes are strictly tangled: as subdiffusion deepens upon increasing the optical force, deviations from Gaussianity in the FnGD regime become larger and more persistent in time. In addition, the distinctive exponential tails of FnGD are quickly built up in the subdiffusive regime. Our results shed new light on previous experimental observations and suggest that FnGD may generally be a memory effect of earlier subdiffusive processes.
新发现的菲克型而非高斯扩散（FnGD）在这里被精细地调整和研究，研究范围广泛，涉及概率和时间尺度，使用胶体珠的准二维悬浮液在静态和空间随机光力学场的作用下。这种实验模型允许人们证明，具有接近自由悬浮体扩散率的“快速”FnGD 区可以源自早期的亚扩散。我们表明，这两个区是严格纠缠的：随着光力的增加，亚扩散加深，FnGD 区的非高斯偏离变得更大，并且随时间更持久。此外，FnGD 的独特指数尾部在亚扩散区迅速建立。我们的结果为以前的实验观察提供了新的视角，并表明 FnGD 通常可能是早期亚扩散过程的记忆效应。
