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Umklapp process

  1. Oct 30, 2013 #1
    This occur when two phonons interact and the sum of their momenta add to a new wavevector outside the new Brillioun zone. The resulting wavevector is then mapped back into the Brillioun zone by subtraction of a suitable reciprocal lattice vector.
    I don't think I understand the physics in all of this. I understand the idea but what is physically going on in this process and where does the leftover momentum go?
     
  2. jcsd
  3. Oct 30, 2013 #2

    UltrafastPED

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    The left over energy absorbed by the crystal; the momentum is not "real momentum" - it is crystal momentum, which is not conserved.

    See https://www.physicsforums.com/showthread.php?t=715639
     
  4. Oct 31, 2013 #3

    DrDu

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    Well, of course also real momentum is conserved. It is taken up completely by the lattice.
     
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