Talk:Plasmon

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In the second paragraph: "... because the electrons in the metal screen the electric field of the light." that doesn't seem to make any grammatical sense, but I may be wrong.

  • Read "screen" as a verb not a noun. ie. the electrons (which are in the metal) are screening the electric field.

Contents

[edit] The initial definition

I don't really think this definition is very clear. Could someone who knows expand on it? Unusual Cheese 13:24, 17 August 2007 (UTC)


Im prety sure a phonon is not just a quantized sound wave, but a quantized vibration, and therefore a quantized mechanical wave

Psylabs (talk) 05:28, 3 April 2008 (UTC)

^^^^^ there are some articles that might be useful. D.Bohm and D.Pines, Phys.Rev. 92,609 (1953) D.Pines and D.Bohm, Phys.Rev. 85,338 (1952) —Preceding unsigned comment added by 58.207.133.126 (talk) 13:36, 11 May 2008 (UTC)

[edit] More screening woes

I still don't understand this use of the word 'screen' even as a verb. As I understand it to screen means 'to examine', 'to block'* or 'to display' none of which fits the context as far as my understanding of this subject goes.

Either I'm being incredibly ignorent or in this particular situation 'screen' is a colloquial term or jargon.


  • If this is the case, 'screen' is not a particularly informative word when related to the physical processes actually taking place.


What is meant is 'screening' as in 'blocking' the electric field. See Electric field screening. I think the description is accurate, but I'm not quite sure. I'll check some refrences over the week-end. O. Prytz 22:53, 6 January 2006 (UTC)


I am more worried about the correctness of the physics. First, shouldn't the plasma frequency of copper be in the ultraviolet as well? Second, I always thought that the colors of metals are mostly due to the positions of their "interband transition" thresholds. Gold is yellow because blue light can cause electronic transitions from the occupied states in the "d band" to the unoccupied states in the "s band", and is therefore strongly absorbed. The same goes for copper, I suppose. See Electronic band structure. Finally, what geometrical factors exactly affect the plasma frequancy of gold? Just asking...

[edit] plasma frequency for some materials

I agree, the plasma frequency should be in the UV also for copper, see e.g. . But the matter seems to be quite complex, especially in the noble metals. The characteristic colour of copper and gold should be attributed to electronic transitions from d-bands to the conduction band. The energy of these transitions are in the blue region, thus both metals appear reddish and yellowish, respectively.

One more remark: The plasmon frequency for semiconductors is usually in the very deep UV, not IR! Around 15-16 eV. That's why they look silverish - like metals. You cannot use the standard free-electron-gas model to calculate the plasma frequency (this is, what gives IR-frequencies). As I haven't digged deep enough into the matter, I won't change the article. But if there is someone more experienced around, please do it! (With some references...) That would be great!

One could be easily mistaken cause phonons give raise to similar effects as plasmons. That's why people refer to IR. And 16eV is volume plasmon energy for silicon and germanium (Ch. Kittel "Introduction to solid state physics" table 2 on page 278). And 16 eV is huge energy, so normally no plasmon can be excited thermally, so there's no screening in IR. One would say that if plasmon frequency is in UV then it should screen IR which is obviously not true.Maybe that's why there is so many controversions about it.

[edit] Plasma frequency in semiconductors and colour of gold

I am changing now the article to reflect the outcome of this discussion, as the current state is wrong for sure.

If somebody feels like adding/correcting more - this is, of course, welcome! —Preceding unsigned comment added by Beathovn (talk • contribs) 13:30, 4 October 2007 (UTC)


I think metals transmitting UV is wrong. I say this looking at the following articles and when I read metals transmitting UV I was really suprised. From reading the below articles I concluded that UV can cause plasmons on metals while visible light doesn't have the energy to cause the quantized electron density oscillation (somehow majority of the light is reflected). The Drude or Jellium model sort of explains why metals are not transmissive compared to a dielectric crystalline material. Now if one uses quantum dot metals the story is different but I haven't read anything on it yet. Also just think about your car. If metals transmitted UV then we would all be baking in a metal car (very simplified imagination). I know the penetration depth for 1um light is ~1.9nm for copper using the equations from any optics book (I used Fundamental of Photonics).

N. H. Matlis et al, Snapshots of laser wakefields, Nature Physics, Vol 2 (2006). Tajima, T. and Dawson, J. M. A laser plasma accelerator. Phys. Rev. Lett. 43, 267–270 (1979). Pukhov, A. and Meyer-ter-Vehn, J. Laser wakefield acceleration: the highly nonlinear broken-wave regime. Appl. Phys. B 74, 355–361 (2002). --NA 13:56, 25 October 2007 (UTC)