Reading the FAQ on how phonons

[xiankai]

after reading the FAQ on how phonons, or modes of vibrations, are responsible for the slowing down of photons in dense materials, i still have some unanswered questions:

i visualise phonons as something like qualities of a field, because they coordinate the deviant behavior of individual particles.

ultimately, is it the particles that absorb and re-emit the photons with the observed characteristics of phonons,

or is it that the phonons are something like gravitational waves (ONLY in the sense that they cannot be directly observed, but their effects are documented); an invisible field that coheres the movement of the photons, such that the actions of individual particles are ignored, but are observed as a 'single entity'

thanksie

 

[inha]

phonons can be directly observed. one can measure phonon dispersion relations with inelastic neutron or x-ray scattering. so although they are collective excitations of the whole many body system they are real in that sense.

 

[denian]

I can provide you with a response to your unanswered questions about phonons and their role in slowing down of photons in dense materials.

Firstly, it is important to understand that phonons are not qualities of a field, but rather they are quantized lattice vibrations in a material. They are collective excitations of atoms or molecules in a solid, and they can be thought of as packets of vibrational energy.

To answer your first question, it is both the particles and the phonons that are responsible for the slowing down of photons in dense materials. When a photon enters a dense material, it interacts with the particles in the material and gets absorbed and re-emitted multiple times. Each time it interacts with a particle, it loses some of its energy and slows down. The phonons play a crucial role in this process by coordinating the interactions between the photons and particles.

Regarding your second question, phonons are not like gravitational waves. Gravitational waves are disturbances in the fabric of space-time, whereas phonons are vibrations in a material. While their effects may be similar in the sense that they cannot be directly observed, they are fundamentally different phenomena.

In summary, phonons are not qualities of a field, but rather they are quantized lattice vibrations in a material. They play a crucial role in slowing down photons in dense materials by coordinating the interactions between photons and particles. They are not like gravitational waves, but rather a unique phenomenon in the world of condensed matter physics. I hope this helps to clarify your questions.