  We study segregation of a binary mixture of similarly charged particles under
shear using particle-based simulations. We simulate particle dynamics using a
discrete-element model including electrostatic interactions and find that
particles segregate according to their net charge. Particles that are charged
twice as strong as other particles of the same electrical sign are seen more at
insulating boundaries with which we shear the system. Weakly charged particles,
on the other hand, stay more in the center of the sheared bed. We propose a
simple model based on electrostatic potential energy to understand this
segregation. The model shows that the segregated system we observe in our
simulations is indeed the most favorable configuration in terms of
electrostatic potential energy. Our simulations further show that for a given
packing fraction there is an optimal shear velocity where the segregation
maximally intensifies. We show that this maximum results from a competition
between diffusional and Coulomb fluxes. For a larger shear velocity, diffusion
suppresses segregation.
