 Mott two-current model

When spin-flip scattering is weak, two spin populations have separately defined current responses and share a terminal electric field. Their electrical conductivities add: $\sigma ={\sigma }_{\uparrow }+{\sigma }_{\downarrow }$, so $\rho ={\rho }_{\uparrow }{\rho }_{\downarrow }/({\rho }_{\uparrow }+{\rho }_{\downarrow })$. Spin-dependent band structure and scattering set the channel parameters; being the majority population does not universally imply lower channel resistivity. The model is named for Nevill Francis Mott and is the independent-channel basis for many giant magnetoresistance models.