ABSTRACT
Mott showed that the scattering rates for up-and down-spin subbands were di¥erent, that scattering between subbands was relatively rare, and therefore that electrons in the two subbands do not intermix. It follows that a conductance gs can be de¢ned individually for each spin subband,
g e DN EF↑,↓ ↑,↓= , 2 ( ) (6.2)
where D is assumed to be the same (in metals) for up-and down-spin carriers. It is clear from Figure 6.1a that g↑ ≠ g↓, and Equation 6.1 can be rewritten as
P g g
g g =
−
+ ≠ ,↑ ↓
( ) ( )
0 (6.3)
by noting that J ∝ g. že conceptually important point is that the electric current in a ferromagnet is the sum of spin-up and spindown partial currents, and these partial currents can be modeled as independent. žis idea is oªen called the “two current model” of charge and spin transport.
