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Phonon-photon interactions: guidelines needed

  1. Jul 4, 2012 #1
    Hi!

    I'd really need someone to tell me if I'm on the right track here. What I need to do is a research on electromagnetic radiation-matter interactions, based on phonon-photon interactions. Does this include any of the following: photoelectric effect, Compton scattering, Rayleigh scattering, Thomson scattering, nuclear photo effect, electron positron pair production?

    As you can see, I'm having trouble comprehending what phonon really is an what role it has in these interactions (if any), but I'm currently searching, so I'll get to that. All I'd need to know right now if I'm on the right track with these effects and scatterings mentioned above: are those based on phonon-photon interactions?

    Oh, and some recommendation of literature would mean a world to me, since I currently have no idea from where to start.
     
  2. jcsd
  3. Jul 4, 2012 #2
    Phonon is a quasiparticle that is associated with a propagating mechanical wave in a crystal due to oscillations of the ions around their equilibrium lattice positions.

    Since a propagating wave makes a modulation of the concentration of the ions, it causes an electric polarization in the solid. This polarization, in turn, is able to affect the propagation of electromagnetic waves, whose associated particle is the photon. The strong coupling between photons and optical phonons leads to a new quasiparticle called polariton.

    As for the terms you had mentioned, I don't think they are related to phonons.
     
  4. Jul 5, 2012 #3
    I think the book NONLINEAR OPTICS is much helpful
     
  5. Jul 5, 2012 #4

    DrDu

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    These effects are all due to photon-electron interaction and don't involve phonons (=lattice vibrations).
     
  6. Jul 5, 2012 #5
    Thank you all so much. Everything is much clearer now - at least I know where I'm heading with this. :)

    Dickfore, you've been very helpful. Here where I study, we've never used the term "polariton", but "light exiton", and that why my search hasn't been very productive.

    Thanks again.
     
  7. Jul 5, 2012 #6

    Cthugha

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    Excitons are another different kind of particle. One may imagine them as a bound pair of an electron and a hole, somewhat similar to hydrogen. These can also form polaritons, so called exciton-polaritons if they couple strongly to light, for example in microcavities.

    The term "light exciton" may refer to the kind of hole which is present in the exciton. Holes can have different projections of the angular momentum on the z-axis (3/2 or 1/2). These two kinds of holes also show different dispersions which can be interpreted as different effective masses in effective mass approximation. Therefore you have one light hole (or just light) exciton and one heavy hole exciton. However, these are not really important in terms of phonon-photon interactions, unless you really have exciton-polaritons.
     
  8. Jul 5, 2012 #7
    "the wave" associated with phonon must be originated from or involved with some interaction(s). But there are only four known interactions: gravitational, electromagnetic, strong and weak. The latter two can be ruled out in this context, so phonon can only be gravitational or electromagnetical in nature.

    If phonon is gravitational, then it must be the long-sought quantum of gravitation (!). So phonon can only be (or mostly be) electromagnetical.

    As a matter of fact, since phonon is the quantum of interaction between the ions of the vibrating lattice and other objects (electrons, neutrons), and such interaction is BOTH gravitational and electromagnetical, so phonon is indeed both gravitational and electromagnetical. Only, the proportion of gravitational phonons is extremely small (may be of the order of square of mass/charge ratio, or so, I am not sure).
     
    Last edited: Jul 5, 2012
  9. Jul 5, 2012 #8
    Please don't misguide the op by invoking unnecessary terms.

    In condensed matter physics, ultimately all the interactions are of electrostatic origin, coupled with the Pauli exclusion principle. Even ferromagnetism is not as much due to "molecular currents" as it is due to Hund's Rules (which originate from the so called exchange interaction).

    What I mean by "mechanical" waves are oscillations of the ions from their equilibrium positions. The role of an effective potential energy is played by a combined effect of the electrostatic Coulomb interaction + the stationary energies of the electrons in the field of fixed ions (1st correction to the Born-Oppenheimer approximation).

    These oscillations may cause a change in density (longitudinal oscillations), but no change in the polarization (acoustic modes), or with a change in the electric polarization (optical modes). The propagation of an electromagnetic wave is strongly modified in the presence of oscillating polarizations. In the language of quasiparticles, there is a strong coupling between photons and optical phonons.

    The gravitational interaction is negligible, and the nuclear forces are limited to distances of the order of the size of a nucleus. Thus these do not play any role in condensed matter physics.

    Please disregard what 'zhanhai' is talking, as it is meaningless.
     
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