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So there isn’t a phonon field? The concept of phonons is confusing because unlike other particles, phonons don’t have an accompanying fundamental field. They
by willis936 7y ago
So there isn’t a phonon field?
The concept of phonons is confusing because unlike other particles, phonons don’t have an accompanying fundamental field. They seem more like an emergent phenomenon. Why should phonons be considered particles?
- empath75 7y agoIt’s a quasi-particle.
- pariahHN 7y agoTotally not a physicist. But, I would guess that it has to do with wiggles in space-time, since they do say it's from the vibrating of the atoms. Energy is transferred through a medium via imparting of wiggles to that medium, so I think it would be reasonable to guess that it's either the vibrations moving through space-time or maybe some other field related to mass.
- plus 7y agoI'm trained in physical chemistry, rather than physics, so I don't have the firmest grasp of quantum field theory, but I think the analogous "phonon field" would be the Born-Oppenheimer potential energy surface (PES). Vibrations, and hence phonons, are collective excitations on the PES.
- danharaj 7y agoThey are particles of an effective field theory which approximates the quantum phenomena in a piece of matter at a particular energy and length scale.
- knzhou 7y agoI used to be annoyed about that, but the particles we currently think of as “fundamental” could well be emergent too. So reserving the word “particle” for only fundamental ones isn’t practical.
- ISL 7y agoPhonons are the minimum quantum excitation of vibration within a material. Just as harmonic oscillators have quantum energy levels, so do materials. You are correct -- they are an emergent phenomenon. In the case of phonons, they can carry momentum, they travel like particles. A sibling comment is correct -- they are technically quasi-particles [1]. It is okay to think about a phonon field within a material. That field is not fundamental, in the sense that an electron is presently-believed to be fundamental, but that doesn't keep it from being a very useful way to think about condensed-matter physics. [1] https://en.wikipedia.org/wiki/Quasiparticle https://en.wikipedia.org/wiki/Quasiparticle
- deepnotderp 7y agoIt's a quasi particle, like a hole in semiconductors. It's a mathematical formalism afaik, not due to an underlying field that it's an excitation of.