Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Featured A Phonon detection

  1. Aug 1, 2017 #21

    Andy Resnick

    User Avatar
    Science Advisor
    Education Advisor

    Phonons are quantized displacements of a crystal (an ordered array of many atoms); a good discussion is in Coleman's "Introduction to Many Body Physics", chapter 2.4.
     
  2. Aug 1, 2017 #22

    DrDu

    User Avatar
    Science Advisor

    Yes. I mean, if they aren't eigenstates of energy and crystal momentum, they are time dependent phonons but phonons nevertheless.
     
  3. Aug 1, 2017 #23

    Mech_Engineer

    User Avatar
    Science Advisor
    Gold Member

    My bad! Carry on... :oops:
     
  4. Aug 8, 2017 #24
    Measurements of the phonon dispersion curves (energy vs. momentum) are very standard in neutron inelastic scattering and to a lesser extent in inelastic x-ray scattering. In these experiments you detect single neutrons and x-ray photons. Each neutron/photon enters the sample will a well-defined energy and momentum (direction), and comes back out with different energy and momentum. The difference is taken up by the phonon, i.e. a phonon is created in the process (or another elementary excitation, e.g. a magnon in a magnetically ordered crystal) . So with each x-ray photon or neutron you measure a single phonon. You need x-rays or thermal neutrons rather than visible light for this because the momentum transfer is on the order of the reciprocal lattice unit.

    http://www.nobelprize.org/nobel_prizes/physics/laureates/1994/press.html
    http://iopscience.iop.org/article/10.1088/0034-4885/63/2/203/meta

    "Thermal diffuse scattering" of x-rays or neutrons is also caused by phonons, but in that case you do not measure the phonon's energy.
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted