Figure 1
Illustration: Alan Stonebraker

Figure 1: (a) In a charge current, spin “up” and “down” electrons flow together. In a spin current, up and down electrons flow in opposite directions. (b) A schematic of the spin Hall effect. Spin-orbit coupling induces an orbital motion opposite in direction to the electron spin, deflecting up- and down-spin electrons in opposite directions. The net effect is a conversion of charge into spin currents.