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Potential and impurities

  1. Apr 1, 2010 #1
    Hi

    1) I have read in an article that the atoms in a lattice are at "half-filling". As I understand, this means that the chemical potential is zero. Why does "half-filling" mean since it equals that the chemical potential is zero?

    2) Lets say that I place an impurity with potential U0 in my lattice. Does it make a difference whether U0 is positive or negative? What is the usual case?

    Best regards and happy Easter,
    Niles.
     
  2. jcsd
  3. Apr 1, 2010 #2
    1) Half filling means every site in the lattice has a single particle. Since each site can hold two particles, you are at helf filliing. The chemical potential being zero is a consequence of having a symmetric band structure and an on site energy of zero.

    2) Yes it matters whether U0 is positive or negative. I think there is no usual case, it depends on what kind of model you want to study.
     
  4. Apr 1, 2010 #3
    Thanks. Regarding #2, if I set U0>0, then it "costs" more energy to be there, right?
     
  5. Apr 2, 2010 #4
    Right
     
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