We are familiar with phenomena like photoelectric effect or excitation of atoms/ions to higher energy states. Such excited atoms/ions sooner or later relax to lower energy levels by emitting light (or X-rays) or -- in solids -- by creating phonons. Yet recently very interesting observations have been made, namely reversal of magnetization in thin ferromagnetic layers under very short (few femtoseconds, fs) pulses of laser light with wavelength around 800 nm. The energy of those photons, expressed in temperature units, is an order of magnitude higher than Curie temperature of the sample under investigation and even exceeds few times its melting point.
While in 'optical' case, i.e. during absorption or luminescence or Mossbauer effect, the process may be explained in purely mechanical terms (photon carry well defined momentum) then the magnetization reversal is a puzzle. The observed reversal seems sensitive to the polarization of exciting light, right- or left-circular or just linear. How the angular momentum of a nonmagnetic photon interacts with magnetic moments of ions?
Dear Marek,
Given the title of your thread, I thought that you were thinking in possible strange behaviors of the photons at certain values of their energies or polarizations. But now with your interesting selection of references I see that your question is much more complex: you are asking about the femtosecond scale photo-magnetic recording. This is nowadays a very important research subject indeed with a great community specialized in this topic. But it is necessary to highlight some remarks with respect to your question (perhaps this was only my personal fault of quick reading).
1. In this effect you never have a single photon as fundamental particle. In fact you have a femtosecond pulse of coherent beam of photons exciting d-electrons within crystalline fields associated to octahedral and tetrahedral lattices.
2. Although the photon is a fundamental particle, the phonon or magnon are not. And the main application of this effect is related with not allowing to have almost no these quasiparticles during the quantum level transition.
3. The photons must be circularly polarized and also linerly under certain situations. This is very important because their electric field is well defined for the interaction with the electronic spins.
4. The transport equation used in this phenomenology is the Landau–Lifshitz–Gilbert where the damping of spins are the main physical object to be excited.
In summary, this scenary is very different that a photon particle even considered within a magnetic ionic background as considered in my first answers. Repeat that there is a big community of magnetism devoted to control this magnetic swiching under the laser light application as the nonabsorptive inverse Faraday and inverse Cotton-Mouton effects. The main technological interest is recording but also in spintronics is open a new window for seeing more general physics.
Contrary to a common misconception, we do not have different kinds of photons for the magnetic and electric fields, as they (E and B) have the same units -- e.g., gauss. It is important, to avoid confusion, to also remember, from SR, that E and B are not independent. The only observer-independent reality (SR included) is the EM field, which has one kind of photon -- the EM photon.
The photon is only quantum of electromagnetic field (some kind of radio wave). There is no moment when the photon is neutral electrically or magnetically. Please see Fig. 2 in the " About Energy of Photon".
Dear Marek,
The measurable photons do not have electric and magnetic fields. They don't interact with a charged or magnetized body.They exist as the superposition of innumerable such energy packets which gives the classical electromagnetic wave's electric and magnetic fields.
Their most known relationship with the magnetic field is the Faraday rotation effect, i.e. the polarization rotation of the photons rotate when they go though a magnetic field. Thus the magnetic moment of the photons doesn't change with the magnetic ions if they do not produce a high magnetic field which only can change the angle of their polarization. But if the magnetic ions produce a stationary magnetic field the conservation of the magnetic moment of the photons must be followed although their polarization could change. Thus I'm quite pesimist to obtain something new of the system that you ask about.
I admit that my question is a bit provocative. This doesn't mean I believe in different kinds of photons carrying electric or magnetic field, no matter that photons are particles with S=1 and thus Sz=-1, 0, or +1. Yet recent observations suggest that magnetization reversal is sensitive to exciting light polarization. Is it possible that magnetization reversal is related only to photon's momentum? Don't we need, during this process, some sort of short living magnetic interaction between photon and magnetic ion spin?
@Daniel: what do you mean when you write ...magnetic moment of the photons... ?
Dear Marek,
The photon has zero mass and obviously its magnetic moment is calculated in a different form that for instance the electron ( a Bohr magneton). In the following reference you can find it well defined
http://physik.uni-graz.at/~dk-user/hallstatt/chavez_hallstatt09.pdf
What strong is the exciting light polarization? Is it enough for having a photon-photon interaction?
a photon wave function may be written as including many terms, it includes electron positron, proton anti proton, due to pair creation,
Ayhan Yuzubenli: The photons were invented long before any antiparticles were discovered and existed in our minds as particles on their own. Why not to let them to stay this way? Additionally, if I remember well: two photons are needed to create electron-positron pair; one is not enough. Even more: infrared or visible photons are unable to produce such pair - their total energy is much too small.
Daniel Baldomir: the presentation you have attached doesn't seem helpful, at least for experimental physicists like myself. I know what is vacuum and what is the magnetic field. OK, combined together they create non-isotropic space. Why should we call such space polarized?
My original question originated from few recent publications (there are other):
1. All-optical magnetic recording with circularly polarized light, Phys. Rev. Lett. 99 (2007) 047601
2. Ultrafast optical manipulation of magnetic order, Rev. Mod. Phys. 82, (2010) 2731
3. Photoinduced Ultrafast Magnetization Dynamics in Yttrium-Iron Garnet and Ultrathin Co Films, IEEE Magnetic Letters 7 (2016) 5201404
3. Ultrafast nonthermal photo-magnetic recording in a transparent medium, Nature 542 (2017) 71
4. Selection Rules for All-Optical Magnetic Recording in Iron Garnet,
Preprint Selection Rules for All-Optical Magnetic Recording in Iron Garnet
Optical phonon's frequencies are an order of magnitude smaller than that of the exciting light, thus "thermal" explanation seems improbable at least. Maybe magnons are at work? But then: how photons create magnons?
dear Marek Wojciech Gutowski for pair production we do not two photons, if photon energy is beyond the total mass enegy of pair particles, pair production is possible, or vice versa when particle and anti particle meets then one photon appears
Ayhan Yuzubenli: no, you can't be right. Imagine a pair particle-antiparticle colliding in their center of mass reference frame. Total momentum is exactly zero. A single photon - if created - should then have null momentum. Do such photons exist? Problem disappears when two photons (with k'=-k'') are created during annihilation.
Dear Marek,
You wrote:
the presentation you have attached doesn't seem helpful, at least for experimental physicists like myself. I know what is vacuum and what is the magnetic field. OK, combined together they create non-isotropic space. Why should we call such space polarized?
Remember that I only have tried to explain your previous question about what was the photon magnetic moment. In simple words if you assume the photon as a boson with spin S=1, by Zeeman within a strong magnetic field B in the vacuum, there is the possibility to induce a photon magnetic moment. My answer was very general and now it would be necessary to enter in the details of how the magnetic ions can give such vacuum and if the frequency of the photons also allows it.
All and DB, MWG: I suggest the book by the well-known Melvin Schwartz, "Principles of Electrodynamics", of 1972. Electromagnetism is deeply affected by SR, E and B are not independent, and must have the same units (already have, in SI CGS). Read review below:
Unlike most textbooks on electromagnetic theory, which treat electricity, magnetism, Coulomb's law and Faraday's law as almost independent subjects within the framework of the theory, this well-written text takes a relativistic point of view in which electric and magnetic fields are really different aspects of the same physical quantity. Suitable for advanced undergraduates and graduate students, this volume offers a superb exposition of the essential unity of electromagnetism in its natural, relativistic framework while demonstrating the powerful constraint of relativistic invariance. ... The rest is online.
In keeping with the linear characteristics of the Maxwell formulation,
photons do not interact with each other to any significant extent, so I agree
with above apreciations as to lack of electric or magnetic properties.
(thoughthere exist a lot of debate about what photons are)
Yes, conservation of momentum does create photons in pairs
by particle anhilation. However they are simply created also with electronic transitions in matter, and absorbed the same way.
In the sense that they can be destroyed or created, not really real particles. Carriers of energy lump,
is their most famous distinction.
The story of Black body radiation is the best I think to understand what one is talking about when we say photons.This was the original
great advance by Max Planck, father of the Quantum. Almost a non beleiver of his own advance to the end of his days.
After emission, how photon propagates? Like a particle or like a wave.
If in partical form how it reach every where?
If in wave form, how it is qunta (photon)?
Ed Gerck
"A single photon at a time, can build an interference pattern."
Curious to know about this in little detail
To Geepack
The photon propagates as electric and magnetic field in the space. The speed of light is only c^2 = 1/ (μ0 ε0) in SI system. In the SI system value of μ is set up by convention. If one presume μ0= ε0 then c= 1/ μ =1/ε.
The photon is a particle in own electromagnetic space. It is a wave in gravity field (space). More in: "New Concept of Space".
About single photon interference.
The photon is a packet of waves. More in: "About Energy of Photon" .
The interference experiment with single packet of waves everyone can see on the surface of water. It is enough to throw a stone in calm water to create a wave pack. When first waves is reflected by obstacle or edge, they interfere.
Dear Marek,
Given the title of your thread, I thought that you were thinking in possible strange behaviors of the photons at certain values of their energies or polarizations. But now with your interesting selection of references I see that your question is much more complex: you are asking about the femtosecond scale photo-magnetic recording. This is nowadays a very important research subject indeed with a great community specialized in this topic. But it is necessary to highlight some remarks with respect to your question (perhaps this was only my personal fault of quick reading).
1. In this effect you never have a single photon as fundamental particle. In fact you have a femtosecond pulse of coherent beam of photons exciting d-electrons within crystalline fields associated to octahedral and tetrahedral lattices.
2. Although the photon is a fundamental particle, the phonon or magnon are not. And the main application of this effect is related with not allowing to have almost no these quasiparticles during the quantum level transition.
3. The photons must be circularly polarized and also linerly under certain situations. This is very important because their electric field is well defined for the interaction with the electronic spins.
4. The transport equation used in this phenomenology is the Landau–Lifshitz–Gilbert where the damping of spins are the main physical object to be excited.
In summary, this scenary is very different that a photon particle even considered within a magnetic ionic background as considered in my first answers. Repeat that there is a big community of magnetism devoted to control this magnetic swiching under the laser light application as the nonabsorptive inverse Faraday and inverse Cotton-Mouton effects. The main technological interest is recording but also in spintronics is open a new window for seeing more general physics.
Dear Daniel,
Yes, yes, yes! Your last message is right to the point; great thanks for much better explanation of my problem to other discussants, including potential ones.
The thickness of magnetic layer is of order of 10-20 nm, while the laser wavelength is ~800 nm. The pulse lasts long enough to produce roughly 1-2 full cycles of oscillations. We certainly are at a verge of quantum mechanical description of this phenomenon, certainly outside the classical Landau-Lifshitz-Gilbert (LLG) description. LLG equation, a differential equation, is not applicable here, I think. It describes nicely the ordinary relaxation processes (the one preserving fixed sign of projection of magnetization vector onto local magnetic field direction) -- but not the magnetization switching. Today we are familiar with relaxation times in range of 10-9 - 10-13 s (corresponding to ferromagnetic resonance frequency, in GHz range), while magnetization reversal occurs within much shorter times (hundreds of THz).
I think the (inverse) Faraday or Cotton-Muton effect is closer to reality than "thermal" explanation but still not fully satisfying. Looks like the switching to quantum mechanical description is a must. That's why a single photon in my original question.
@Ilgaitis Prusis: you comments are interesting - but what is their relation with magnetization reversal by light?
The photon is generally both electrically and magnetically neutral in a long time period. But in short periods one can see quick replacement of electric field by magnetic field and vice versa. More in:
Article About Energy of Photon
Therefore photons are highly active both magnetically and electrically. Colours fade in the light, window curtains lose strength, many substances simply collapse and should be kept in the dark.
Ilgaitis
@Ilgaitis Prusis: To make it short: your article discusses plane electromagnetic wave, not photon. Maxwell's equations have other solutions, in form of knotted fields, much better localized. Those, however, are most likely related to ball lightnings -- quite big objects when compared with atoms.
@Marek. There are many experiments witch show that photon is only EM wave. The photon can be generated by radio means, trapped in the resonator, transmitted by waveguid etc. Radio waves can be polarised like photons and so on. Difference is only in frequency. There are two spaces simultaneously for photon. In the electromagnetic space the photon is like ball (knotted field), in the ordinary gravity space the photon is wave. It is the cause of wave-particle duality.
The standing wave in resonator is not a (single) photon, which never rests. The description of electromagnetic phenomena in terms of plane waves is mathematically perfect, but physically somewhat bizarre and confusing. Photoelectric effect, as well as gamma rays, cannot be described correctly as an action of completely delocalized plane waves. On the other side, assigning a single frequency to any given photon (including those making ELF -- Extremely Low Frequency, i.e. below 1 kHz and with wavelength exceeding 300 km) seems mathematically strange. Interestingly, photons with well defined energy are not controversial at all.
Coming back to the original question: reversal of magnetization of a given ion seems to be a single act, not the result of gradual amplification (resonant?) of its (thermal?) vibrations. Spontaneous remagnetization also happens, but only at sufficiently high temperature, even in absence of photons.
Suppose! On a day, only one (single) photon released from the Sun direct in the line of The earth,
1) Will it reach the earth?
2) If yes, will we see some light on the earth, if yes, Will it be seen at all the Sun shining are of that time?
To Marek on ...The standing wave in resonator is not a (single) photon, which never rests...It is myth. The photon can have any speed from zero and above. Please see Lene Hau experiments: "Physicists Slow Speed of Light" https://news.harvard.edu/gazette/story/1999/02/physicists-slow-speed-of-light/
She slow down photon to zero speed and then accelerate up to c. In a metamaterials speed of light can be from negative to superluminal.
You wrote about math problems to describe a photon in different environments (gravity space and electromagnetic space) with the same equations. It is not a problem of physics. In gravity space one must use wave equations. In other spaces is useful describe photon as particle. For physics math is only set of tools. In the one case one use a spade, in other is useful a raker.
Best regards
Ilgaitis
@Preston Guynn: Your papers deal with electrons, protons and neutrons. Very impressive numerical results, indeed. Unfortunately near nothing about photons, but also about Bohr' magneton or nuclear magnetons, or ... positrons. Did you try to publish your findings?
@Deepak Bhalchandra Gode: I don't see any relation to magnetic phenomena in your questions. Haven't you mistaken the thread?
@Ilgaitis Prusis: Please read the mentioned reference carefully. It is the light, not photons, what is slowed down in described experiment. The light propagates slowly within the condensate but nothing is said about its speed after it leaves this special chunk of matter. You may think about this phenomenon in terms of old-fashioned index of refraction, if you like. It is just extraordinarily high for Bose-Einstein condensate, that's all. Or the other way: a light (wave) is like an ideal gas, which can move quite slowly as a whole while the speed of its atoms (here: photons) remain unaffected.
@Marek no definitely, answer to the questions I asked leads to EM field, you or any one answer it.
Dear all:
I don't know whether my answer will contribute or not to the main objective of this question since is a simple answer, but since is a fundamental idea i got motivated to recall it...
Photons does n't have Eectric Charge.
So, they cannot interact in any means with EM fields. There is no way a Phonon (which in definitions is by itself the EM Field) can interact with itself, since it does n't have Electric Charge.
There is no other way fundamental particles can interact with the EM field than by having Electric Charge.
Hope it contributes, Regards !
I'm speaking witchin the frame of QED and QFTs of course ... not in the scenarios of Classical Optics or Quantum Optics
@Franklin Uriel Parás Hernández: your answer is certainly valuable, thank you. But, at least for me, it is also very problematic. Indeed, the photon carries no electric charge. Do you mean that the photon is only a purely mathematical object, good for description of (real) time-dependent electric and magnetic fields? Without any contact with physical reality otherwie? No electric charge then no magnetic field, right? How about photon's electric field then? The indisputable formula for photon's energy says it is proportional to \omega, i.e. angular frequency. Frequency of what, if not the EM field? Now I'm really lost ...
Maybe the solution of this mystery is somehow related to photon's spin??
Only proton and electron are rotate, and they carries electric charges.
Yes, Izetali, there is fundamental connection between charge and rotation. See, for example, solutions for charged and rotating black holes. They are the same.
To answer the question one should know spatial EM structure of a photon, as well as the dynamics of its electric and magnetic field components. My attempt to look deeper at the nature of photon is here:
Article On the Nature of Photon
Dear Marek Wojciech Gutowski
I don't think that the fact the Photon carries zero Electric Charge should mean it cannot be a real particle. The Electric Charge is no requirement for a particle (or a field) to exist as a real particle. Lets take the examples of Neutrinos, Dark Matter, Gluons, the Higgs Boson itself, all of them have zero Electric Charge and we can detect them (directly or indirectly) (except directly, for Dark Matter, yet) in experiments as real physical effects on Matter, or other particles.
But maybe I'm understanding your point well. Can you explain in more detail why a zero Electric Charge could lead to the conclusion of Photons just be virtual particles?
"No electric charge then no magnetic field, right?"
Well... Electric Charge and Fields are two separated things, maybe a more correct statement shoub be:
"Particles with no electric charge don't interact with magnetic fields, right?"
If so, is it right, if a particle (like the Photon) doesn't have Electric Charge is impossible (by the rules of QED) that this Photon to interact with any Electric or Magnetic Field.
This is the reason of one of the fundamental things between QED and QCD.
In QCD (Quantum Chromodynamics) the field which is the responsible for the propagation of the Strong Nuclear Force is the Gluon. The Gluon doesn't have Electric Charge, but do have "Color Charge", which is the Quantum Charge (or Quantum number) which is associated with the coupling between the Quarks and the Gluons (this latter, the responsible for the Nuclear Strong Force). Because the Gluon does have Color Charge, does interact with itself (in total contrast with the Photon and the EM Field) and in the case of QCD, the Gluon Field interacts with itself and this is the reason why the effect of the Nuclear Force gets to a such tiny distances (roughly the size of a Proton).
But in the case of the Electromagnetic Force and the Photon: The Photon (or better said the EM Field) which is the responsable for the EM force in the universe, since it doesn't have Electric Charge, it doesn't interact with itself and it doesn't get "screened" by itself. This is the reason why in QED the effect of an EM Field can be non-zero up to an infinite distances (this is the theory of course)
The Energy of the Photon still being E=hf (or E=h*nu), the point here is to take the approach on the Photon and the EM Field being the same thing. The Photon is the EM Field in a quantized frame.
So, since the EM Field can vibrate when we accelerate an Electric Charge in this field, then it can have a finite frecuency of oscillation, so the Photon too, which is not more than the particle-like approach of the Physical Nature.
The Spin of Photons is related to its modes of Polarization.
Hope it helps
Kind Regards ! :)
Dear Franklin,
It is well known that the photon is a fundamental particle that doesn't carry electric charge. And also think that is absurd to analize the nuclear interactions for answering this question made by Marek. By the way, although the gluons haven't photons because they belong to the SUc(3) symmetry (therefore there are 8 gluons instead of a gluon) in QCD, however the photon and the gluon can be related in the electroweak interaction with symmetry SUw(2)×Uy(1) (within the Standard Model). In any case in any case, the worry of Marek is about a femtosecond pulse of coherent beam of photons exciting d-electrons within crystalline fields associated to octahedral and tetrahedral lattices. That is to say, the electronic structure of the solid is the only responsable interaction and never the long-ranged gauge interactions action in the atomic nucleus.
There is a post here in this thread May 17th where there are more analysis made on this interesting issue purposed in the thread.
The photon is only quanta of EM wave. Average value of electric and magnetic fields are zero, but instant value not. There are rapid change of electric fields from + to- and change of magnetic poles from N to S. The photon is highly active both magnetically and electrically. More in: Article Nature of Photon
All: Is reality something meaningful? And is natural science steadily coming closer to a true depiction of it? These two questions are obviously related and belong very much to the domain everyone here can contribute, qua mind-independent reality. But some people here insist in staying in a mind--dependent reality, also known as psychosis.
Transitions between electron energy levels are usualy associated with photons, not phonons. Addition of heat, the
rise in temperature can be associated with more phonons in
a crystal lattice.
A single photon has not associated magnetic field.
Electromagnetic fields are macroscopic phenomena.
Juan Weisz
Juan: everything depends on which photons (and which electronic energy levels) we are talking. In electron paramagnetic resonance, the signal (absorption) goes down at very low temperature. This is called, from more that 50 years, phonon bottle neck.
What will be the Lorentz transformation with v=c, Ed?
I mean the magnetic field of light.
EFK and all: Light in vacuo travels at v=c, and is the only case. The Lorentz transformation applies up to that limit, as close as desired to v=c, or does anyone still think that infinity exists in nature? Then, the value at v=c becomes the value at a neighborhood of v=c, as close as desired. It is certainly bounded.
Alternatively, one can do an analytic continuation in the complex plane. Look up in my home page at RG, current, on the uses of complex numbers in physics and engineering.
QUESTION: Who deserves the right to judge the physical correctness of the particular choice of the branch of the square-root?
EFK and all: Continuing, and contrary to a common faulty reasoning, we do not have different kinds of photons for the magnetic and electric fields, as they (E and B) have the same units -- e.g., gauss. It is important, to avoid confusion, to also remember, from SR, that E and B are not independent. The only observer-independent reality (SR included, but not QM yet) is the EM field, which has one kind of photon -- the EM photon.
Of course, SR means the Minkowski SR as used in physics, not the Einstein formulation of SR, which has further inconsistencies.
Joachim
In physics you often have to choose which branch of a square root is relevant.
ED
I already tried to argue with you, you never answer directly without citing some other work
Do you think that if I write
f=qE
and
f=q v cross B
that since the force on the left has the same units,
why should E and B on the right have the same units.?
You think everyone using SI units is wrong?
JW and all: Not only I think that everyone who uses the E and B in the SI units have no idea it is basically wrong, their conclusions are also. Read M. Schwartz in 1970, book op. cit., or Sean Carroll at Caltech, recently, or others. Doubting it is not credible, nor reasonable. This is not just an opinion, or my opinion.
Well, I think we all agree that photon carries no electric charge and is a quantum of EM field. Oscillating field, i.e. having electric and magnetic component varying in time with known frequency. My original question is: what is the amplitude of its magnetic field?
MWG and all: The magnetic field is caused exclusively by charge in motion. In a referential where the charge is in motion, it radiates an EM wave. That EM wave is made out of photons, exclusively, with no charge, and can be 100% reabsorbed by a charge, even by the same originating charge, in two processes, completing the only 3 processes of interactions of photons in QM, as postulated by Max Planck and calculated by Einstein's A and B coefficients.
A photon, then can exhibit one of the 3 behaviors when meeting a charge: absorption, emission, and stimulated emission. The last causes the laser to exist, macroscopically. Emission, then, can also be named "spontaneous emission" or simply emission, and "stimulated emission", to highlight their common process. Absorption, likewise, can be called "absorption up" or simply absorption, and "absorption down" as stimulated emission. Here, with incident photons, up arrows can represent photon absorption, while down arrows can represent photon generation.
Dear Marek:
This is what I think:
The amplitud is a characteristic of waves, not of particles (I'm not considering the probability of locating a mass particle in a given position in space (Wave Function in the Schrödinger Eq.), though the Schrödinger equation is not valid for photons).
I think the question is not well defined:
A Magnetic's Field amplitud cannot be associated to a single photon, since the concept of photon is a full particle-like description, and there is no wave characteristics involved.
The only properties a photon can have are particle-like properties -which are properties that are defined univocal for a given point in time and a given point in space, not a range of values as we commonly do for the localization of waves in space-
A photon can have particle-like characteristics:
- Spin, polarization (quantum state of polarization, not wave polarization), helicity, etc.
So, I think is not good to mix the different physical descriptions we have for nature. In some experiments is more convenient to use the wave description of light, to better explain our results of the experiments, in other scenarios; the particle-like description. But I cannot think one scenario where you will need to explain some phenomenon using both kind of properties e.g. the wave amplitud or intensity of the light and particle-like properties as the spin or the mass of the particle.
And if it is so, then you probably need to pull a hand out of Quantum Field Theories, like QED in this case, and then you may be able to work with wave-like properties again. But in this time; quantized wave-like properties, which is the most valid description of nature we have so far... this would be in terms of the lagrangian density and potentials fields, etc...
Best Regards !!
Ed: I'm not sure your picture is always correct, maybe in the vacuum containing a single charge. You completely ignore spin as a source of magnetic field (yes, original Maxwell's equations do not have such a component). If a charge (electron, with spin=1/2) emits photon (with spin=1, curiously - something doesn't fit here) then this very photon cannot be reabsorbed as those two will never meet! A charge is simply too slow, at least when its mass is non-zero. Do you suggest that there is no magnetic field related to a given photon (the same for electric field)?
FUPH and all: There are no two descriptions we have for nature. Nature is neither particle nor wave, it is a quantum, a third (often neglected) description of the two-slit experiment.
This explains, for example, that the same pattern is formed for weak fields, when there is only one photon at a time, incident on the two slits, and why one cannot detect "the" mythical slit that the photon uses (as it uses both). See video op. cit., for example.
Dear Marek:
That is exactly what I suggest, as I tried to mean before:
There is not a Magnetic field and Electric field associated to photons, because the photons are the EM field.
is like to try to ask ourselves: What is the strength of gravity of a graviton? is n't a well defined question, because... the Graviton is the Macroscopic description that we see as gravity, both things are the same...
Or like to try to associate .. What is the amount of Heat a phonon can carry out? , is not well define too, because the Heat itself is the Phonons.
Well, is what I think, in terms of the reductionist approach.
Regards !
Dear Ed Gerck:
I know what you mean, I didn't say there are two real descriptions of nature. What I tried to say is that we physicists use different descriptions of the same physical concept/object when we have to explain an observed result or phenomenon in different experiments. But of course we have done this for the entire history of science. But I know, at the most reductionist level of physical reality, it must be one and only one description of it. But this is all part of the point I'm trying to prove here.
:)
MWG and all: Electron spin (pictorially said) is not an exception of the movement of a charge, it IS its movement along its axis -- the movement of a charge. If you abandon this simple pictorial view, spin can be different than unitary (in whatever units one fancies) + or -. There is no magnetic field related to a given photon (the same for electric field) -- the only entity that has real significance is EM (where E and B have the same units, e.g, gauss, in SI CGS, are not independent, and obey Minkowski SR). This is the understanding in physics, for 70 or more years. It is not a personal opinion, or my opinion (I was not even born then).
FUPH and all. Old-time (or not careful) physicists have used different descriptions of the same physical concept/object when they had to explain an observed result or phenomenon in different experiments. This is incorrect, but can be justified, for example, by calling out different ranges of energy or time. It uses the concept of boundary, a fictional construct (although it can follow real lines) in thermodynamics (See Joseph Kestin well-known book, for example).
BTW, as said first by Dirac, a photon only interferes with itself, and yes, a photon can be re-absorbed 100% by the same electron that created it.
Multi-photon process also exist, see my listed publications for examples with excimer lasers in the UV creating laser emission (strong) in the blue-green range in any of three atoms in a periodic Group.
Well, Ed Gerck , not just Old-timers, we continue to do this all the time,
Take the example of the phenomenon called as Superconductivity. 'Till the last decade, important and crucial discoveries have been continuously made in this field. We still in the times when we still don't know what is the real description/explanation of the phenomenon which explain the so called High Temperature Superconductors, even so, we continue approaching it with a particle-like description theory: in terms of the Copper Pairs, from the BCS Theory. And at the same time, there is other group of scientists who are trying to explain this same phenomenon using pure QFT, the so called pure Condensed Matter Physicists, moreover using descriptions pulled out of "rare" fields of physics as String Theories, Quantum Information and Quantum Holography ... But untill the phenomenon isn't clear, we will continue trying to approach to the same observations from different theories or different descriptions. We do this all the time in Condense Matter field.
And, I personally dont think this is wrong, I believe that the more descriptions we can have to a same observation, the better the understanding we will be able to gather from the same observed physical phenomenon, even so if we know that it has to exhibit a single-description nature.
At the end, the definitive killer experiment must arrive, and lean the scale in the direction of one of the theories, this is when that theory becomes the leading theory, and then is when we now know which one should be the only valid description to describe what is happening ... at least for the moment (scientific theories never should reach to the point as being consider as ultimate truths).
Kind Regards !
FUPH and all: You refuse to acknowledge that what you said is not what is used today, when duality has been proven wrong. Make a boundary on that, be more careful now, and this becomes another one of those fruitless controversies on RG, like JW and others insist to hold, perhaps to gain RG points, but being tagged. There are no waves or particles in nature, quantum won the description, but one can use waves or particles as a model -- albeit limiting the conclusions. Let us play billiards?
The experimental fact is that light is able to switch magnetization in thin layer of YIG (yttrium iron garnet). So, at least in my opinion, there must be some magnetic field present there, isn't it? As you say, photons do not have any magnetic field - so what is going on? On the other hand, a photon is nothing else but your beloved quantum particle. Do you have any sensible explanation of cited experimental fact?
MHG and all: Everything is already solved in nature, otherwise it would halt. Nature hasn't halted in 14 billion years. The answer you seek is not one I seek, I am just happy to have helped on the joy of finding things out, even maybe just a bit. You may focus better your question.
Dear Marek,
Magnetic moment of ion is the vortex of the electromagnetic field near ion. The photon is two coupled vortexes. Your phenomena are interacting of vortexes.
If you will have some free time, please look at the pictures in the book "Electromagnetic Gravity. Part 1" in my profile. You may see the animation of photon on my sight http://gravity.spb.ru
Yours
Valeriy Pakulin
Nothing particularly special-though, currently, it's possible to do interesting experiments on single photons: https://iqst.ca/quantech/research/fock.php
A photon is the one-particle state, created from the vacuum, by the corresponding creation operator. From there it's completely straightforward to compute the corresponding magnetic field, its expectation value in that state. Electrodynamics, in the absence of matter, is a free theory, so all quantities can be computed exactly.
Though it should be noted that, since photons don't carry electric charge, they're not the sources, but describe the configurations, of a magnetic field.
The applications to the photoelectric effect and all the rest, that's mentioned in the followwup text, are completely irrelevant for answering the main question.
The magnetic field, in any case, is a gauge invariant quantity, it's, just, not Lorentz invariant, so it's an intermediate quantity, anyway, for computing the physical quantities, that are both, gauge invariant and Lorentz invariant.
This is a standard homework problem in quantum field theory and is presented in any textbook.
@Stam Nicolis:
We use ordinary candles, or - more recently - lasers to obtain/generate photons, not some mysterious creation operators. Anyway, when you write it's completely straightforward to compute the corresponding magnetic field, then I think you are able to tell us how strong is photon's magnetic field. Please, reveal this number to participants of this thread (a sensible formula will do as well). But then I will ask you how far from the photon is this "number" valid.
Ed
No one is wrong. WE know that to weigh the value of
E and B fields relative to each other means the inclusion of
appropriate physical constants, but you are not obliged to use
Gaussian units. To use Gaussian you include a factor of
1/c in the Lorenz force law. (compensates v dimensionally)
SM and all: In the case of the photon, there is no charge to create a EM field in movement, or when the photon is absorbed, nor if stimulated emitted. And yet, a high-power laser can create an electrical spark in air, or access a magnetic transition's dipole moment. How?
First, there is NO magnetic field of a photon in SR or QED. From there, it's also NOT possible to compute the corresponding magnetic field of photon, for the same reason you can't compute its electric field alone -- all one can compute is the EM field. Electric and magnetic fields are not independent, even for an electron (see above). E and B fields are components of the EM object, and must have the same units.
Marek, In our work, a photon is a fiber that oscillates and twirls in the same planes perpendicular to its propagation, thus it traces a waveform during translation, but it is not be a wave unto itself. Although it is not a spherical particle or wave, it will exhibit wave-particle duality in an interferometer. Photons with shorter oscillation strokes (greater frequency) have more energy per Planck. Per Maxwell, the photon has B & E properties caused by its oscillation and twirling motions. Its twirling motion is supported by recent research from Spain.
Due to the photon's B-property, it can interact with a magnetic dipole field and cause it to reverse.
Regards
Hello Marek,
I am reminded, by your question, of the experimental work undertaken by Mary Somerville (1780-1872) to try and confirm a magneto-optical effect whereby exposure of a dimagnetized steel needle to violet light caused it to become magnetized. Her paper on this effect was published in 1826 in the Philosophical Transactions of the Royal Society of London.
If you saw the movie "Mr. Turner", about the great English landscape artist, there is a scene in which the Mary Somerville character, played by Lesley Manville, demonstrates the effect to Turner and his father. She takes a steel sewing needle and hammers it with a wooden mallet to demagnetize it, then she exposes it to violet light by way of a prism, and then demonstrates that the needle has been magnetized - I believe - by showing that it lines up with the Earth's magnetic field by floating it on water and watching it orient itself accordingly. Note, the Germans during WWII used the wooden mallet technique to demagnetize the steel frame of the V1 buzzbomb surrounding the missile's magnetic compass before setting the compass' heading towards its intended target.
Anyway, the effect was difficult to reproduce, although, it did excite quite a bit of interest in Wollaston, one the Herschels (father or son, I don't remember), Maxwell, and Faraday. Of course, Faraday eventually discovered the magneto-optical effect whereby glass exposed to a magnetic field changed the direction of polarized light - the Faraday effect.
Somerville's most noteworthy accomplishment was her translation into English of Laplace's "Mecanique Celeste". For a very interesting biography of her, see the following book: Robyn Arianrhod; Seduced by Logic; Oxford University Press; 2012. You can find a description of Somerville's magneto-optical experiments on pp. 223-226.
I know all of this does not answer your question, but I thought that you might find it interesting nevertheless.
Regards,
Tom Cuff
Looks like with still have no clear explanation of the so called inverse Faraday effect, known since more than 190 years (big thanks to Thomas Cuff for recalling Mary Somerville's experiments!). Unbelievable!
If not in photon language then, maybe, this phenomenon could be better described in terms of ordinary electromagnetic waves?
Just a moment ago I have seen the new paper, here on RG:
Preprint All-optical spin switching under different spin configurations
It says nothing about photon's magnetic field but nevertheless explains spin switching (i.e. magnetic effects) caused by light. Highly recommended for participants of this thread!
All: Note that I rely on RG for notifications of postings, rather than looking directly to more than 5,000 different pages. RG, however, has failed to notify many, many occurrences, it seems to have problems, or it hits their covert anti-congestion system.
If that happens to you, and I don't reply, this may happen because of RG failure or anti-congestion, because I have already replied earlier in the archives then RG hid it and it is a repeat question, because your question is off-topic or judged out of line, such as almost all ad hominem attacks, or because I am waiting for others to reply so that I am not trying to monopolize the space offered free of charge by RG. Anyway, to reply is optional here, but eventually most messages are read, even if not replied.
Now, if you are classified as a fantasy poster, the message will just be ignored by the filters. The suggestion is, don't get into those filters -- it may be permanent.
Is the helicity of the photon connected with the charge interaction mechanism?
Because of the Bose distribution in Black body radiation you know the photon spin
is 0,1,2,3,...but if it is 1 there must be a reason. Ive heard of helicity (coordination with momentum) but not magnetic effect in the case of the photon. I think reactions with particles is where the conclusion comes. ie, consevation of angular momentum on both sides of a reaction.
Am I correct?
@Juan Weisz: photon's spin, Sz = -1, 0, or +1 (but not 2, 3 or more), corresponds in wave picture to linearly or circularly polarized light (cw or ccw). Indeed, some recent reports suggest that magnetization switching by light is sensitive to the light polarization.
Per Science-Daily: Photonic molecules are formed when individual (massless) photons "interact with each other so strongly that they act as though they have mass". In an alternative definition, photons confined to two or more coupled optical cavities also reproduce the physics of interacting atomic energy levels, and have been termed as photonic molecules. ["Seeing light in a new light: Scientists create never before seen form of matter". Science-daily.com. Retrieved 2013-09-27.]
Many experiments and research in multiple countries have shown that formations of strongly interacting photons can constitute matter [i.e. see above]. These experiments were usually done using 'light' photons in simple laser interactions or in laser interactions in optical cavities.
Since matter is matter regardless of how it is created, it can be suggested here that an extremely dense mixture of photons [dense like the experiments] in the early universe may have strongly interacted with each other creating formations of matter. Such dense mixture would have included the entire spectrum of photons from the radio to the gamma ray. Thus, each originally created subatomic particle would have contained a mixture of photons instead of only 'light' photons used in the experiments. Thus, these particles would be more stable than than those created in the experiments.
See pages 21 and 22 in the link that examines the magnetic dipole field of an electron, which is a cylindrical B-field [CBF] composed of strongly interacting, twirling and oscillating photon fibers per Figure 9. Each disk of the CBF only consists of a single photon fiber. The dipole field of a photon is similar to that of the electron's dipole field except it only loops around a single disk instead of a series of disks in the electron as shown in Figure 9. The photon's dipole field can interact with a macroscopic dipole field and change its polarity.
The link is much easier to read if it is downloaded rather than viewing it on RG's site.
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