4 Quotes by Joe Orenstein

Spin Coulomb drag results because the motion of spin through the semiconductor is sensitive to collisions between electrons, whereas the transport of charge is not. When electrons bump into one another, the mutual repulsion of their negative charges creates a drag on their spin current, which is a relative motion between individual electrons, but not on their charge current, which is the collective transport of all the electrons in motion.

We get a diffusion of spin because we create a situation in which there will be more spin-up electrons in one place and fewer in another.

The fact that spin current is not conserved may be bad news, but the important thing is that we know what is going on. Things may not have gone as predicted, but at least we've expanded our knowledge base in an area that we didn't know much about before.

You would think that since an electron carries a spin and a charge, that their motions would be equal. But, our research shows the contrary, due to a friction-like effect known as spin Coulomb drag.