Drude model

  1. As far as I understand: In the Drude model we take the electron to be moving in a random direction after each collision (*), such that the mean velocity is simply the average of -eEt/m, which is just -eEτ/m, where τ is the relaxation time.
    But Im very confused about this basic assumption (*), if the electron has a velocity in the direction of the field and suffers collision with another electron, it does not seem likely that the direction of the velocity of the 2 electrons after collision will be completely random.
  2. jcsd
  3. UltrafastPED

    UltrafastPED 1,912
    Science Advisor
    Gold Member

  4. That was quite helpful. Now I don't suppose you could help me interpreting another
    l) states that the equation for the displacement of a Fermi sphere is (all h's are hbars):
    h(d/dt + 1/τ)δk = F
    Now Newtons law for a completely free electron is:
    hdk/dt = F
    Why have they put in a δk, and how is the equation to be interpreted? Does it represent the motion of the Fermi sphere in steady state?
  5. UltrafastPED

    UltrafastPED 1,912
    Science Advisor
    Gold Member

    Probably the variation of k ...

    You would get more attention by posting a new question.
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