  We report results from the molecular dynamics simulations of a binary
colloidal mixture subjected to an external potential barrier along one of the
spatial directions at low volume fraction, {\phi} = 0.2. The variations in the
asymmetry of the external potential barrier do not change the dynamics of the
smaller particles, showing Arrhenius diffusion. However, the dynamics of the
larger particles shows a crossover from sub-Arrhenius to super-Arrhenius
diffusion with the asymmetry in the external potential at the low temperatures
and low volume fraction. Super-Arrhenius diffusion is generally observed in the
high density systems where the transient cages are present due to dense
packing, e.g., supercooled liquids, jammed systems, diffusion through porous
membranes, dynamics within the cellular environment, etc. This model can be
applied to study the molecular transport across cell membranes, nano-, and
micro-channels which are characterized by spatially asymmetric potentials.
