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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 7: Emerging Topics in Chemical and Polymer Physics, New Instruments and Methods I
CPP 7.2: Vortrag
Montag, 9. März 2026, 11:45–12:00, ZEU/0255
Non-local diffusion model as a description for non-Gaussian diffusion in scattering experiments — •Harish Srinivasan1, 2, Veerendra Kumar Sharma2, and Subhankur Mitra2 — 1Institute of Applied Physics, University of Tübingen, Tübingen, Germany — 2Solid State Physics Division, Bhabha Atomic Research Centre, Mumbai, India
We introduce a non-local diffusion (NLD) model that provides a unified theoretical framework for describing non-Gaussian diffusive dynamics in fluids. The NLD formulation generalizes conventional diffusion by incorporating a jump kernel, enabling analytical characterization of van-Hove self-correlation functions with exponential tails. This framework naturally connects two major classes of anomalous transport observed in scattering experiments: non-Gaussian fractional Brownian motion (nGfBm) in sub-diffusive glass-formers, and Fickian yet non-Gaussian diffusion (FnGD) in cage-jump dominated liquids. In the nGfBm regime, the NLD description captures the crossover from non-Gaussian to Gaussian sub-diffusion seen in molecular and polymeric glass-formers [1]. In the FnGD regime, the NLD model predicts the exponentially fast approach to Fickianity and the much slower algebraic restoration of Gaussianity [2]. Comparison with incoherent quasielastic neutron scattering data across multiple systems demonstrates the universal applicability of the NLD model and establishes non-local diffusion as the common physical origin of non-Gaussian signatures in molecular fluids. [1] H. Srinivasan et. al., Phys. Rev. Lett. 132, 058202 (2024) [2] H. Srinivasan et. al., arXiv:2504.15020 (2025)
Keywords: Anomalous transport; Brownian motion; Neutron Scattering; glass-forming liquids; supercooled liquids