Course F: Classical Drude Model

How do we derive the Drude model?

start from Newton’s laws of motion

remember $F = -eE$ (E = field)

Take time avg of t and v₀

Electron flux in classical Drude model $J$

$$J = -nev$$

$v$ = drift velocity

-ve as velocity opposes conventional current flow

drift velocity

average electron velocity

mobility

drift velocity per unit field

$$\mu = |v| / E$$

Define conductivity in terms of mobility

$$\sigma = ne\mu$$

ability of charge carrier to move in electric field

How can we apply the Drude model to monovalent metals?

what assumptions do we make?

find velocity using KE = $\frac{3}{2}k_BT$

assume mean free path = interatomic spacing ~ 1nm

then find $\tau$ using speed = distance/time

assume 1-2 e- per atom

Lorentz force $F_y$

$$F_y = -ev_x\times B_z$$

Force due to electric field on electron

$F = qE$ where $E$ = field

What does the sign of the Hall coefficient tell you?

e- = -ve

h+ = +ve