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Quasimomentum concept

  1. Dec 24, 2014 #1
    Why momentum of phonons called quasimomentum? Is it due to the fact that wavenumber of vibrations confined in a first Brillouin zone, and therefore can not have an arbitrary value as "usual" momentum?
  2. jcsd
  3. Dec 25, 2014 #2


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    The momentum of phonons isn't called quasimomentum. The true momentum of phonons is 0. While the true momentum is a consequence of translational invariance, quasi- or crystal-momentum is a consequence of the permutational symmetry of the atoms in the underlying crystal. See Ashcroft and Mermin, specifically one of the appendices.
  4. Dec 30, 2014 #3
    needed that info thanks
    Drdu will there be a gain in entropy of phonons , or heat from the movement of phonons
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