Dear all,
Out of question 2.3 and 2.4 of the Drude model follows that the free path of the electrons is independent of the temperature. Here I think I have missed something. Why is the free path in the Drude model independent?
Thanks for everybody who tries to help me
Is it true that \tau is a constant? I understand why the free path \lambda does not depend on the temperature T if \tau is constant. So again, is it true that \tau always is constant in the Drude model?
This all because if \tau is constant, then
\lambda = v \tau
\lambda is constant IF \tau is independent of the temperature T. Is it true that in the Drude model is assumed that \tau is a constant independent of T?
v is always independent of T if \tau is constant. This because v= \frac{-e \tau}{m}E=-|\mu|E. (v and E should be a vector.) All those constants are independent of T if again \tau does not depend on T.
The question is mainly about the limitation the Drude model faces if one doesn’t consider Fermi statistics. Imagine there is a finite concentration of impurities in a material and electrons scatter every time they hit one of those. If one forgets about Fermi statistics, the electron speed will depend on temperature, and therefore the colder the material, the more the scattering time. This, however, isn’t what happens in real materials.