Magnetic nanoknots evoke Lord Kelvin's vortex theory of atoms

June 23, 2017 by Lisa Zyga feature
Simulations of magnetic skyrmion knots with Hopf charges of (a) 3, (b) 6, (c) 7, and (d) 10. Credit: Sutcliffe. ©2017 American Physical Society

(Phys.org)—In the late 1800s when scientists were still trying to figure out what exactly atoms are, one of the leading theories, proposed by Lord Kelvin, was that atoms are knots of swirling vortices in the aether. Although this idea turned out to be completely wrong, it ushered in modern knot theory, which today is used in various areas of science such as fluid dynamics, the structure of DNA, and the concept of chirality.

Now in a new paper published in Physical Review Letters, mathematical physicist Paul Sutcliffe at Durham University in the UK has theoretically shown that nanoparticles called magnetic skyrmions can be tied into various types of knots with different magnetic properties. He explains that, in a sense, these nanoknots represent a "nanoscale resurrection of Kelvin's dream of knotted fields."

Skyrmions are the name of a general class of particles that are made by twisting a field. When this field is a magnetic field, the skyrmions are called magnetic skyrmions. Magnetic skyrmions have attracted a lot of attention recently due to their potential applications in spintronics, where electron spins (which are related to the electron's magnetic properties) are exploited in the design of transistors, storage media, and related devices.

Magnetic skyrmions were experimentally observed for the first time a few years ago, in thin slices of magnetic materials—basically two-dimensional materials. By showing that magnetic skyrmions can theoretically be tied into knots, the new results move these particles from the two-dimensional world to the three-dimensional one.

"The most significant point is that these nanoknots are stable, because usually fields avoid being knotted by untying themselves," Sutcliffe told Phys.org.

Sutcliffe showed that the skyrmion knots can be characterized by the Hopf charge, which indicates the number of times that a skyrmion's curved magnetic lines are linked with each other. He showed that skyrmions with low Hopf charges tend to form rings, while those with higher Hopf charges form links and knots.

Sutcliffe's investigation focuses on magnetic skyrmions in a particular type of magnet called frustrated magnets, which offer skyrmions an additional rotational degree of freedom compared to other magnetic materials. This flexibility gives skyrmions the extra room needed to be tied into knots.

At the time Sutcliffe was writing his paper, no one had ever observed skyrmions in frustrated magnets. But as a testament to the fast pace of research in this area, just a few days after this publication researchers from China reported the first experimental observations of skyrmions in a frustrated magnet (arXiv:1706.05177 [cond-mat.mtrl-sci]).

This result marks an important step toward realizing knotted , and the next challenge will be to find a way to engineer the skyrmions into knots. Recent work on skyrmions has suggested that these particles may be controlled using optical vortex beams, arrays of ferromagnetic nanorods, and other methods. Researchers are also currently developing imaging techniques for skyrmions, which will be essential for the identification of these nanoknots. With new results on skyrmions being reported almost daily, Sutcliffe is optimistic about the prospects of creating knots.

"My future research plans in this area are concerned with studying the formation of these nanoknots, to help develop methods and suggest favorable conditions for experimentalists to create and observe these structures," Sutcliffe said.

Explore further: Neutron scattering clarifies the arrangement of skyrmions in material

More information: Paul Sutcliffe. "Skyrmion Knots in Frustrated Magnets." Physical Review Letters. DOI: 10.1103/PhysRevLett.118.247203 . Also at arXiv:1705.10966 [cond-mat.mes-hall]

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12 comments

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Dingbone
Jun 23, 2017
This comment has been removed by a moderator.
rrrander
5 / 5 (2) Jun 24, 2017
I remember some nutjob, a janitor or something, who'd concocted a similar theory of atomic structure.
Dingbone
Jun 24, 2017
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Dingbone
Jun 24, 2017
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Dingbone
Jun 24, 2017
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swordsman
5 / 5 (1) Jun 24, 2017
Lord Kelvin's "Plum Pudding" model was intended to be correlated to electromagnetic radiating waves. That, as it turns out, is fairly accurate. He moved his spoon back and forth and observed the physical waves and compared them to the waves of electromagnetic fields. It does not appear that this would produce "knots" as described above.
Dingbone
Jun 24, 2017
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Dingbone
Jun 24, 2017
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AGreatWhopper
3.7 / 5 (3) Jun 25, 2017
The article is about magnetic skyrmions, not some batshit crazy rejigging of a century old debate that hasn't been for a very long time.

Just report Dingbat and don't feed the trolls. And read one of the much better sites that don't have every nutjub on the planet drooling their wisdumb every damned article.

If you really want to save the world from self-impressed idiots, the EU convention is right around the corner. You can collar all the idiots you like. August 17-20, Phoenix. If confronting pseudo-science and outright fraud is really your passion, you must do it. If you settle for feeding the trolls on here, then you're just as sick, sad and sorry as they are.
RealityCheck
1 / 5 (4) Jun 25, 2017
@AGreatWhopper.
Just report Dingbat and don't feed the trolls. And read one of the much better sites...
It would help the forum members greatly if you could post your real name and your list of "better sites" you recommend instead of PO. That way they can gauge better your credibility in this matter; as you attempt to censor.bias science discourse on the net, according to what YOU deem 'acceptable science'. Oh, and before again calling others "nutjobs", it would help your own cause if you first proved to yourself/forum that someone calling themselves "AGreatWhopper" is not the one who is the real "nutjob" in the case. In any case, reality is passing you by. The recent mainstream astro/cosmo/QM physics discoveries/reviews have been proving some of those whom you call "nutjobs" CORRECT all along. So maybe you should listen/learn for a change, @AGW, instead of trying to censor/bias science discussion on the NET. Only 'real whoppers' of a "nutjob" would try that today! :)
swordsman
not rated yet Jun 26, 2017
In reference to my comments above and the response by Dingbone, let me clarify more exactly what Lord Kelvin actually claimed, He pictured electromagnetic waves in the "luminiferous aether" as being stronger than steel and demonstrated the wave effect by waving a stick back and forth in a bowl of jelly, creating semicircular waves that he said are to electromagnetic radiation. In fact, we have known for quite some time that electromagnetic waves from a transmitting antenna appear quite similar to his picture. The leading comments by the author of this article are misleading.
Dingbone
Jun 26, 2017
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