Talk:Phonon

message: I think the simulation on 1D phonon is very helpful for beginner to have a better understanding of lattice waves. It would be better if the author can clarify that the mode depicted is a longitudinal mode. Also, is the simulation depicting mono-atomic crystal or diatomic crystal? It seems that sometimes the "atoms" come too close to one another, which does not happen in real systems because of strong repulsion between atoms when they are less than one atomic diameter apart.WingkeeLEE 02:13, 22 June 2007 (UTC)
replies: text: Odd electrons per unit cell means half full bands in band theory, which tends to make better conductors. Full bands don't contribute to conduction. Almost full bands contribute holes, for a positive Hall coefficient.  Gah4 (talk) 07:47, 13 July 2019 (UTC)
thread_title:  On 1D normal mode 

message: I have read this article a few times and still only have a vague concept of phonons.  Can we get some more detail (and layman's explanations) on these sections:
"According to a well-known result in classical mechanics, any vibration of a lattice can be decomposed into a superposition of normal modes of vibration."
Can we link to an article about this rule, or give a short explanation if none exist?
"Secondly, we treat the potentials V as harmonic potentials, which is permissible as long as the atoms remain close to their equilibrium positions. (Formally, this is done by Taylor expanding V about its equilibrium value.)"
The link to screened in the sentence above this one helps explain it, but the link to harmonic oscillator doesn't really explain to me what a "harmonic potential" is.
"As we shall see in the following sections, any wavelength shorter than this can be mapped onto a wavelength longer than a."
This seems similar to aliasing in discrete-time sampled signal processing.  If the analogy is close enough, should it be mentioned?  Also, analogies to vibrations in strings would help me in particular, but I don't know how close these analogies are, and if they would give the wrong idea.
I guess the rest I don't understand simply because I don't know quantum mechanics... - Omegatron 14:26, Jul 21, 2004 (UTC)
:I think some of these have been addressed, but the entry definitly still needs some work (I'll see what I can do ;-). I like the aliasing analogy, it's exactly right (the points where the atoms are placed act like the points (in time) where the analogue wave is detected in digital streams.) --H2g2bob 02:10, 16 December 2005 (UTC)
thread_title:  Please elaborate 

message: Shouldn't "k" be "k_sub_n" in the exponents of the two Fourier relations immediately following the "One-Dimensional Phonons" subheading?
Marcusl 15:58, 15 February 2006 (UTC)
thread_title:  correcting small erro 

message: If one models air and air molecules as a lot of billiard balls in constant chaotic motion, then how does sound propagate through air?  Are phonons associated with nitrogen and oxygen molecules, as they are with metal molecules?   It seems it would be sort of Rube Goldbergian (like the board game Mousetrap) for sound to be carried and transferred between so many billiard balls in constant chaotic motion, when one is speaking to someone across the room.  
I have read that air molecules at room temperature move about as fast as a jetliner; and that the average path lenght of an air molecule at room temperature is less than a meter. User: McTrixie --71.124.219.87 17:20, 27 August 2006 (UTC)
thread_title:  Billiard ball model of the atmosphere 

message: I hoped to find here something about phasons which apparently are a special case of phonons existing in more complicated (e.g. incommensurate) structures.    At a recent discussion on  quasicrystals they were descibed as a misunderstanding, with the suggestion that 'phason' is in fact an adjective (and thus 'phasonic' is a pleonasm). Perhaps phasons should be mentioned briefly here and linked to separate article that somebody will write.195.96.229.83 10:12, 23 February 2007 (UTC)
thread_title: Phasons?

message: ¿why always the masses are the same in the solution of phonons? In many systems, the masses
are not ordered neither the same.
The mass used is that of the crystalline unit cell which will always be the same.  If the masses are not ordered you do not technically have a phonon since the whole concept is dependent on the existence of a perfectly ordered unit cell periodic in all directions.  —Preceding unsigned comment added by 24.30.105.9 (talk) 07:45, 15 November 2007 (UTC)
thread_title: Different masses?

message: Would standing waves be Hermitian ?
Is this article supposed to be in sync with the French one?
Arnero 05:55, 1 September 2007 (UTC)
thread_title:  Hermitian 

message: In the dispersion relation section there is talk of a diagram, however I don't find it depicted in the article. I think including it would be very helpful in better understanding the section.  —Preceding unsigned comment added by 86.198.1.156 (talk) 07:53, 30 October 2007 (UTC)
thread_title:  Diagram in dispersion relation 

message: Someone did a search-and-replace and replaced all instances of 'phonon' with 'photon', both in the article and the discussion page. I have fixed this. Nightrose (talk) 23:47, 10 June 2009 (UTC)
thread_title:  Vandalism 

message: The explanation of quantisation of wavelength for phonons arising because of the lattice spacing seems simple enough, but I can't understand why this necessarily leads to quantisation of phonon energy. Why can a phonon of a given wavelength not take on a range of amplitudes (and hence a range of energies)? Andipi (talk) 11:50, 16 August 2009 (UTC)
replies: text: E=hf and so E=hc/lambda as c=f*lambda, hence the energy is constant for each given wavelength. HiraV (talk) 15:02, 16 November 2009 (UTC)
replies: text: I had exactly the same question and after reading (what I could of) the article was starting to think energy wasn't quantised at all for phonons, which seemed pointless. Not until I got here did it make any sense. I agree with your comment below - the opening leads the reader down the wrong path and I think it needs to be improved (I would say "fixed" but the whole crystal lattice and diagram thing made sense to me).--Adx (talk) 09:38, 1 June 2010 (UTC)
replies: text: Increased amplitude mean more phonons in the same quantum state. (Remember, they are bosons.) As usual for QM descriptions, macroscopic sized objects have very large N (number of atoms, and so possible modes), and at normal temperatures, the modes are well populated. The quantum steps are small enough to look continuous. At low temperatures, quantum effects are more visible. Gah4 (talk) 08:05, 13 July 2019 (UTC)
thread_title:  Quantisation 

message: I think the page should be started differently; phonons are defined not as the modes of vibration but the quanta of energy that these modes carry - this may lead to confusion. Phonons are to lattice vibration as photons are to electromagnetic radiation - individual fundamental quanta of energy. Should I change the opening of the page? HiraV (talk) 15:02, 16 November 2009 (UTC)
thread_title:  Definition 

message: I do not support the suggestion that the discussion of lattice vibrations and light scattering should be transferred to this general page on the description and mathematics of phonons. The brief description of thermal motion in elastic solids is essential there in order to develop a complete understanding of the mechanisms of Brillouin scattering (& sound absorption) by density fluctuations and microstructural defects in condensed matter. As pointed out there, light scattering has made possible the study of molecular processes from time intervals as short as 10−11 sec. This is one particular application amongst a number of subjects related to phonon transport. 
Thus, there is no reason to support this merger. Rather, the main page on phonons should be clearly referenced there. logger9 (talk) 04:20, 25 June 2010 (UTC)
thread_title:  No Merger from [[Light scattering]] 

message: The header asks for references. I have twice put in 'reliable' ones to Kittel and Mattuck but kbrose keeps removing them without giving reasons - does anyone know of his reliability as an editor?  RedAcer (talk) 13:07, 7 March 2011 (UTC)
replies: text: The reason was stated in edit summaries. Your references did not support your essential claim, that phonon are not quasiparticles, but this is rather common and I added just one reference of a recent text that supports the claim explicitly, many other could be cited as well. Kbrose (talk) 17:25, 7 March 2011 (UTC)
replies: text:  What is rather common? Have you read Mattuck ? You also removed the reference to Kittel which is a good introduction for anyone learning about phonons-this was not a reference to quasiparticles. Please read my comments on the quasiparticle page. To refer anyone to that page will utterly confuse them. Surely the phonon article is not for research scientists who may be able to disentangle the confused definitions of quasiparticle. I agree that usage may have changed and I have started a thread on sci.physics.research(moderated). I suspect that part of the confusion is due to the quasiparticle concept coming from quantum field theory and while these concepts can be used in solid state physics they are not needed for a basic understanding of what a phonon is. You also removed my words saying that a 'phonon is a quantum of energy in a normal mode', this is essential to understanding the concept and now appears nowhere in the article. If no-one disagrees I will put this back in and remove references to quasiparticle until that article has been cleaned up. RedAcer (talk) 19:37, 7 March 2011 (UTC)

text: The article states that it is a quantization, which makes this quantum aspect just as clear. Quantized excited states are commonly referred to as quasiparticle, and this is referenced usage. Virtually every quantum mechanics text use the term. Kbrose (talk) 19:50, 7 March 2011 (UTC)
thread_title:  References 

message: An edit on September 22 by user Cesaranieto (see copied details below) seem to have made a large difference to this section of the article. For example, the user added new/extra notation including l_k = \sqrt{\hbar/m\omega_k}, that is not at all necessary and changed the operators from a's to b's for no obvious reason. The most troubling change though is the definition of the ladder operators. I have worked out the commutation relation for the operators as defined and it does not give the correct value. With the old definition of the a's, the commutation does work out correctly such that [a_k, a_k^{\dagger}] = 1. Of course, it is possible that I made a mistake, and I have been unable to find a suitable primary source containing the answer. Nonetheless, unless someone can explain why the change was made, I will revert to the original version tomorrow.
The offending change (if I judge correctly, my mediawiki-fu is not too strong)
 22:58, 22 September 2012‎ Cesaranieto (talk | contribs)‎ . . (34,165 bytes) (+173)‎
Micah Stoutimore (talk) 01:01, 16 October 2012 (UTC)
thread_title:  Interpretation of phonons using second quantization techniques 

message: A lot of the results on this page (animations, dispersion relations) seem to have to do with lattice vibrations in general. I think it might be nice to have a separate article that discusses lattice vibrations in general (acoustic vs optical vibrations, Brilloin zones, dispersion etc.), so that the phonon article can deal with issues that specifically involve the quantization of lattice vibrations. This would be analogous to how there are separate pages for electromagnetic radiation and photon. Nanite (talk) 13:36, 29 January 2014 (UTC)
replies: text: I agree, it will be great for the readability of both articles and make it easier to structure all the information. JanJaeken (talk) 10:11, 30 January 2014 (UTC)
thread_title:  phonons and vibrations, quanta and waves 

message: It would be nice if this article could have more information explaining how to distinguish these types of modes when looking at a phonon dispersion spetra. For instance I've been told that acoustic modes always start at zero frequency at k=0 due to Bose symetry. Also there is typically LO-TO splitting so the TO mode is at lower frequency (in salts, one can prove the LST relation). I've been told LO modes typically have a larger slope than TO modes. It's hard to find reference that prove these points hold in general, though. I've heard a good reference is "electrons and phonons" by Ziman, but I don't have access to it at the moment. Danski14(talk) 22:10, 23 February 2015 (UTC)
thread_title:  LO vs TO vs LA vs TA 

message: A recent article mentions “First proposed by Albert Einstein in 1907, phonons are packets of vibrational energy emitted by jittery atoms.” which seems to contradict or at least require an additional citation on the origin of phonons.
Article on recent advancements using phonons as a microphone which includes the mention of Einstein: https://m.phys.org/news/2019-07-physicists-particles-quantum-microphone.html
I have not researched this claim but opening up discussion on future changes to this page. Listre (talk) 21:16, 29 July 2019 (UTC)
thread_title:  Reference to first mention considered 

message: An editor has identified a potential problem with the redirect :Phononic Computing and has thus listed it for discussion. This discussion will occur at Wikipedia:Redirects for discussion/Log/2022 May 12#Phononic Computing until a consensus is reached, and readers of this page are welcome to contribute to the discussion.  1234qwer1234qwer4 19:59, 12 May 2022 (UTC)
replies: text: The field is just taking off. Why was it deleted from this article? https://phys.org/news/2019-05-phonon-mediated-quantum-state-remote-qubit.html Hcobb (talk) 20:33, 12 May 2022 (UTC)
thread_title:  "Phononic Computing" listed at [[Wikipedia:Redirects for discussion|Redirects for discussion]] 

message: A recent edit indicates that single phonons are not detectable, but a web search finds many papers on them. It is convenient that many photons have energies that we can detect, especially in the visible optical range. Partly that is because a single molecule in our eye needs to detect one. But low energy photons are not individually detectable, such as those at radio frequencies. And for phonons, higher frequencies are individually detectable, and low frequency ones not detectable. Gah4 (talk) 05:36, 10 June 2023 (UTC)
thread_title:  single phonon detection 

message: The introduction tells us, without citation, that the concept of phonons was introduced in 1932 by Soviet physicist Igor Tamm. Does anyone know which publication this refers to?
On the other hand, the book Twentieth century physics, Vol. I (p.1302) tells us that the name phonon was introduced by Frenkel in his 1932 book Wave mechanics: Elementary theory to ridicule the notion of a photon. If someone has access to that book, it would be interesting to know exactly what Frenkel writes on the subject. Jähmefyysikko (talk) 06:14, 10 June 2023 (UTC)
thread_title:  Origin of the name 

message: I removed: However, photons are fundamental particles that can be individually detected, whereas phonons, being quasiparticles, are an emergent phenomenon. For those interested, the removed reference is here. Gah4 (talk) 09:05, 28 February 2024 (UTC)
thread_title:  Individual detection