  A crossover from a non-Gaussian to Gaussian sub-diffusion has been observed
ubiquitously in various polymeric/molecular glass-formers. We have developed a
framework which generalizes the fractional Brownian motion (fBm) model to
incorporate non-Gaussian features by introducing a jump kernel. We illustrate
that the non-Gaussian fBm (nGfBm) model accurately characterizes the
sub-diffusion crossover. From the solutions of the nGfBm model, we gain
insights into the nature of van-Hove self-correlation in non-Gaussian
subdiffusive regime, which are found to exhibit exponential tails, providing
first such experimental evidence in molecular and polymeric glass-formers. The
results of the model are substantiated using incoherent quasielastic neutron
scattering on glass-forming deep eutectic solvents.
