Physicists trace origin of electromagnetic interaction to Dirac equation

October 12, 2015

An international group of physicists has traced the origin of an electromagnetic interaction to the Dirac equation, a fundamental equation of quantum physics.

The interaction couples the spin of the electron to the of the and it is responsible for a variety of phenomena in a large class of technologically important materials. University of Arkansas researchers proposed the interaction in 2013.

In addition to charge, electrons have spin. By understanding and using the different states achieved when an electron's spin rotates, researchers could potentially increase information storage capacity in computers, for example.

The new finding, published as a rapid communication in the journal Physical Review B, advances the fundamental understanding of magnetic systems as well as multiferroics, which can change their electrical polarization when in a magnetic field or when in an electric field. The rapid communications section of Physical Review B, a journal of the American Physical Society, is devoted to the accelerated publication of especially important new results.

"Through this interaction, magnetic moments can generate an and an electric polarization can generate a magnetic texture in multiferroics," said Laurent Bellaiche, Distinguished Professor of physics at the University of Arkansas. "This provides another handle on how material properties can be tuned or controlled for practical applications in devices based on electrical and magnetic properties."

Surendra Singh, professor of physics, and Bellaiche were part of the U of A team that proposed in 2013 that the angular momentum of an electromagnetic field can directly couple to the spin of an electron to produce a physical energy. This direct coupling explains known, subtle phenomena in magnetoelectric materials and predicts effects that have not yet been experimentally observed.

"For a long time, scientists explained these effects by using only the so-called spin-orbit coupling," Singh said. "Our paper shows that the angular magnetoelectric interaction also contributes to these effects and that this term, along with spin-orbit coupling, follows naturally from a more exact theory of electron-light. It just had been ignored for so long."

The results were obtained through a collaborative effort with two other groups – Ritwik Mondal, Marco Berritta and Peter M. Oppeneer at Uppsala University in Sweden and Charles Paillard and Brahim Dkhil at Ecole Centrale of Paris in France.

Explore further: Physicists reveal novel magnetoelectric effect

More information: Relativistic interaction Hamiltonian coupling the angular momentum of light and the electron spin, Phys. Rev. B 92, 100402(R) – Published 11 September 2015

Related Stories

Physicists reveal novel magnetoelectric effect

February 12, 2014

( —New research at the University of Arkansas reveals a novel magnetoelectric effect that makes it possible to control magnetism with an electric field.

Ultrafast uncoupled magnetism in atoms

September 10, 2015

Future computers will require a magnetic material which can be manipulated ultra-rapidly by breaking the strong magnetic coupling. A study has been published in Nature Communications today in which Swedish and German scientists ...

Probing electron behaviour at the tips of nanocones

February 5, 2015

One of the ways of improving electrons manipulation is though better control over one of their inner characteristics, called spin. This approach is the object of an entire field of study, known as spintronics. Now, Richard ...

Recommended for you

Novel light sources made of 2-D materials

October 28, 2016

Physicists from the University of Würzburg have designed a light source that emits photon pairs, which are particularly well suited for tap-proof data encryption. The experiment's key ingredients: a semiconductor crystal ...

Changing semiconductor properties at room temperature

October 28, 2016

It's a small change that makes a big difference. Researchers have developed a method that uses a one-degree change in temperature to alter the color of light that a semiconductor emits. The method, which uses a thin-film ...

Shocks in the early universe could be detectable today

October 27, 2016

(—Physicists have discovered a surprising consequence of a widely supported model of the early universe: according to the model, tiny cosmological perturbations produced shocks in the radiation fluid just a fraction ...

Bubble nucleus discovered

October 27, 2016

Research conducted at the National Superconducting Cyclotron Laboratory at Michigan State University has shed new light on the structure of the nucleus, that tiny congregation of protons and neutrons found at the core of ...


Adjust slider to filter visible comments by rank

Display comments: newest first

1.2 / 5 (5) Oct 12, 2015

This paper explains the magnetic effect of the electric current from the observed effects of the accelerating electrons, causing naturally the experienced changes of the electric field potential along the electric wire. The accelerating electrons explain not only the Maxwell Equations and the Special Relativity, but the Heisenberg Uncertainty Relation, the wave particle duality and the electron's spin also, building the bridge between the Classical and Quantum Theories. New ideas for interactions and particles: This paper examines also the possibility to origin the Spontaneously Broken Symmetries from the Planck Distribution Law. This way we get a Unification of the Strong, Electromagnetic, and Weak Interactions from the interference occurrences of oscillators.
Oct 12, 2015
This comment has been removed by a moderator.
2 / 5 (4) Oct 12, 2015
Consider the Poynting vector in a 4D space. Present definition does not define the velocity of the field. The Poynting vector about any charge carries the normal vector at a point of the sphere, 1/r^2, about the charge + the Poynting vector of the charge. Spin is an illusion!
The Prof
1 / 5 (4) Oct 13, 2015
Well stated, Hyperfuzzy! Problem is; the rest of the world is too well indoctrinated to see the proverbial 'Wood' from the 'Trees'!
2.3 / 5 (3) Oct 13, 2015
The velocity of an electromagnetic wave can be measured. In fact, it was measured precisely in the year 1936.
When those waves are plotted in space and time, the results conflict with most of the theories of present day quantum mechanics, which is all over the place in reporting conflicting results. Confusion reins!
1 / 5 (1) Oct 13, 2015
The confusion is rather bizarre, the propagation constant, lambda nu = c has nothing to do with the relationship of any field relative to any point in space time. The "speed" of light is an unknown. Obviously if one is trying to measure time dilation would simply change distance and time, but is not relevant. The Dirac function, however is very useful, I used it to help define the propagation of a Gaussian beam in an inhomogeneous medium. I knew that if I used a larger order I might be more definitive, but never precise without a better definition of the actual point motion. The best speed we can derive is: Lambda.emitted /
3 / 5 (2) Oct 13, 2015
Anyway, spin can only be approximated as a tiny charge moving about a sphere, or circular motion, no matter how small the sphere becomes, it is angular motion, not spin; so calling spin as something different than angular motion is redundant, of course it's the same thing. Something like the slit experiment. Particles create waves. Same experiment, same source. An experiment misinterpreted. Obviously a PhD can see this or at least correct himself after 100 years. We, all, are not misinformed. Some of us have moved beyond the 20th century, it's like trying to prove the earth is flat, by example, using only the plains!
1 / 5 (2) Oct 16, 2015
Anyway, spin can only be approximated as a tiny charge moving about a sphere

Spin is an illusion!

Some of us have moved beyond the 20th century

Well done on all but this:

Obviously a PhD can see this or at least correct himself after 100 years.

Unfortunately atoms are still modeled as nuclei with orbitals,as opposed to moving points of charge about which there is an energy flow. You'd think the whole "electron cloud/electron shell" thing might demand a re-do of a model that shows spheres orbiting a central mass.
And you'd think that spheres orbiting a central mass without gravity being involved might suggest that the phenomenon isn't restricted to the quantum regime.

That's why only "some" have kept up.
1 / 5 (2) Oct 16, 2015
Well stated, Hyperfuzzy! Problem is; the rest of the world is too well indoctrinated to see the proverbial 'Wood' from the 'Trees'!

Sorry prof, that was supposed to be a '5' rating.
1 / 5 (1) Oct 16, 2015
All jokes aside, it is a rather complex problem. Consider a unit hyper-sphere. Why would any action within this sphere be different from action within an infinite hyper-sphere? In other words, scale. If the "+&-" occupy no volume then ... ??? The idea is an infinite number may exist within a unit hyper-sphere. Hence should we consider our infinite space as simply a unit sphere? This infers a mathematical 5th dimension but is only isomorphic to reality. Don't want to make the same mistakes of the past by given names to what we do not understand. Hence the little "+&-" ... still working to define a proper space, so far it is not E's or CERN's. You may simply use Maxwell everywhere. But the real game is the definition or explanation of the "+&-", not by collision!

Note: Normalization!
1 / 5 (1) Oct 16, 2015
Its always the fields of the collective centers, both positive and negative and exist everywhere for these particles are neither created or destroyed! Relative to each, the field is perfectly spherical, wither in motion or stationary. Acceleration and motion everywhere is continuous, has been continuous, and will be contentious. All collections seek a stable state. Any point in the field may be modeled as another point located at "r" such that E is the same and the direction is always normal to the sphere at that "ghost" point. The field may be defined at each point alone the time-line based upon change of position among 0-, 0, 0+. Our "space" may be modeled as a 4D space, unitless, i.e. unit -->ct
1 / 5 (1) Oct 16, 2015
Therefore, everything may be defined as the supposition of only the "+" field and the "-" field at each [x1, x2, x3, x4]! Then we will let the computer check out Dirac's brilliance.

But then he wasn't seeking truth, he just wanted to get close; didn't have the tools! That's what discovery is, use what you've got! But don't let old tools slow you down.

And please use logic. You can't use the thing your are trying to prove as your only instrument of proof without supplying an alternative, at least a diametrical argument with a non-existence proof, or som'n som'n ... professional paper, but I would reject it, based upon the title. maybe, rename! In fact, time travel ... what would you rename?

Now where was I, oh the normal of the hyper-sphere? Simple, any line through the center ...
not rated yet Oct 16, 2015
Why not simply define each particle as some sort of magnitude * unit-hyper-sphere, or ... memory/time, hmmm, smart memory!
1 / 5 (1) Oct 16, 2015
But the real game is the definition or explanation of the "+&-",

Remember Feynman slapping the desktop? It eludes a lot of people that things don't pass through other things due to the field present in the "space" between particles (it isn't the particles that prevent this). That although magnetically neutral on the classical scale, on the quantum scale any lattice is a structured magnetic field holding the visible(energetic) components of the lattice in place.

+/- dictates all locations of energy, how it moves (oscillates), how it flows (current). Temperature dictates how quickly this motion happens. Hence why every lattice has an optimum tensile strength at a specific temperature. It's no coincidence that the more +/- you have in an atom the denser and therefore more massive the atom is, mass is a product of charge density.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.