A lot of people are making a point of the "quasi-particle vs particle" distinction. Other than an actual monopole particle being a never-before observed thing, would there be any actual difference in the use and application of a monopole particle vs a monopole quasi-particle?

In other words, should we expect that this discovery (and the apparently previously discovered monopole quasiparticles) have the exact same use and application as a hypothetical normal particle monopole?

Well, my understanding is that some theories of physics predict the existence of monopoles, and some say they can't exist. Finding a real monopole would have an impact on our understanding of physical reality, whereas this is more like an incredibly impressive engineering achievement right? (I could be misunderstanding what the researchers have done)

Yeah, it seems like it doesn’t break theory, but it’s a potentially useful product instead, and folks are disappointed.

They are very different. These are just emergent magnetic charge distributions in certain materials. Real north and south particles would be like magnetic ions. Really weird batteries and magnetic circuits would become possible.

Ok… this still needs to be duplicated, but if it is confirmed it is somewhat of a big deal.

They’re not “real” monopoles, in the sense of individual particles that generate a divergent field but rather a quasi-particle (the collective behavior of many individual atoms producing this overall effect).

In the worlds of the authors:

“These monopoles are a collective state of many spins that twirl around a singularity rather than a single fixed particle, so they emerge through many-body interactions. The result is a tiny, localised stable particle with diverging magnetic field coming out of it,” said co-first author Dr Hariom Jani, from the University of Oxford.

That being said, the applications are still pretty exciting and this is something that many people wouldn’t have tought possible at all.

Others have claimed that quasi particle monopoles have been discovered before. So why would this be somewhat of a big deal if real/duplicated?

The article mentions the significance of them being in Hematite, a naturally occuring mineral.

Correct, this is part of research going back about a decade.

https://www.nature.com/articles/nmat3905

So the only context I have for monopoles comes from the Ringworld books and stories (I'm pretty sure that was it).

What are the actual uses?

I can't get the article to load, if that's in there.

Inflationary cosmology leans a lot on the existence of magnet monopoles.

Why is this, if you don't mind?

One practical one would be super fast computer memory

Video games will be more realistic.

Perpetual motion machine. Make a ring of monopoles all facing one direction along the circumference of the ring. Put a 2nd ring of opposing monopoles inside facing the opposite direction along the ring.

If that would work with magnets it'd work with electric charges.

Stupid question. If you develop a quasi-particle monopole, which I guess is something that is not a monopole but behaves like one, can you use it in such a configuration and get the behaviour you are describing?

This is 2d monopoles on the 2d surface of a material.

This is equivalent to propping up a horseshoe magnet with the ends up, and laying a piece of paper across it; that also gives you a 2d surface with a pair of monopoles on it.

It's still interesting and probably useful for building things, but it's not "we broke a known law of physics".

Your analogy would imply that the other pole exists, it's just someplace else.

Is that what the paper is suggesting? I didn't see that, but admittedly most of it went over my head.

I don't think the paper cares, since it's about how the fields on the surface behave locally while the other pole needing to exist (and of course it could be split into multiple weaker ones, or smeared out, or whatever) is an invariant that applies to the object as a whole.

> They’re not “real” monopoles, in the sense of individual particles that generate a divergent field but rather a quasi-particle (the collective behavior of many individual atoms producing this overall effect).

Can this be replicated on the macro scale with meta materials?

Clickbait. Real monopoles would be an enormous deal. This is… moderately interesting.

"""this is the first time we’ve actually seen a __two-dimensional__ monopole in a naturally occurring magnet ...

These monopoles are a collective state of many spins that twirl around a singularity rather than a single fixed particle, so they emerge through many-body interactions. The result is a tiny, localised stable particle with diverging magnetic field coming out of it,"""

So do I take it that there is some kind of superposition of spins that locally, possibly just in a 2D cross section, appears to have a magnetic field with non-zero divergence? Is \nabla\cdot\vec{B} actually violated somewhere? The language seems pretty cagey.

Incidentally, I belive Dirac posited that they existence of magnetic monopoles would explain the quantization of charge.

From the other thread where this was discussed:

  In the "Emergent Magnetic Charge" section, second paragraph:
  "Finally, we emphasize that the observation of emergent monopoles is fully consistent with the modelling of AFM topological textures in Fig. 2 and does not violate Maxwell’s equation as they are, in fact, sinks and sources of the H^ field."

  So this is a collective effect of a bunch of magnetic dipoles, and they go on to describe how div B is indeed zero in the material.

https://news.ycombinator.com/item?id=38549099

So this is not a Maxwell's Equations violation or anything, it's just some 'trick' to make a field that somehow locally looks divergent.

Yes, it’s a superposition of spins such that the resulting effect is the non-zero divergence

(not a physicist) Dirac proposed a sufficiently long and narrow solenoid would behave as if each end was a magnetic monopole. If the math says it works, then it should be possible in nature.

Please correct my understanding if you know better and I'm wrong.

Something like this happened back in 2014: https://www.nature.com/articles/nature12954

[dupe]

Some more discussion: https://news.ycombinator.com/item?id=38548002

So, who gets to tell J.C. Maxwell?

sounds like room temp superconductors

This feels like it shoud be bigger news. What's the catch?

Magnetic monopoles aren't entirely new in the realm of quasiparticles. We've known about them for quite some while.

Not actual monopoles but quasiparticles

their magnetic monopole quasi-exists

seems like some sort of virtual or model-like result based on emergen properties

The replication crisis, probably

That's a good instinct to have. The answer is that quasiparticles can cover a multitude of sins. My personal Four Horsemen are:

-Quasiparticles: We select some property by drawing a box around a set of adjacent particles and computing over those particles. That property is not represented in a single and unattached member of that box. It isn't the real thing but might approximate some nifty functions you wanted if scaled up and embedded in the right material under the correct circumstances.

-"...in a simulation": This means that this is only as good as your programming (and databases and libraries) is, on top of how well that programming relates to the math you think represents the system in question. Not only do you not have the real thing, you have bits representing the answer to your imperfect programming based on what you think the math is (and what math can be ignored) in your model.

-Analogue of in another system: See sonic black holes. Parallels are drawn between math in one system and math is an entirely different system. Some expect that new inferences can be drawn from the comparison, but you still don't have the real thing, you have a cardboard box with subdividers and you wonder how that applies to high-rises.

-Property exists in n-dimensions: Where N is not our three spatial dimensions. It's not the real thing because we don't have anything with just two spatial dimensions, or an extra spatial dimension, but maybe, just maybe, that can lead to some interesting properties on the edge of the thing, or its face, but probably not in the way you would expect.

Listen for their hooves during any breathless science press release about physics, materials science, and so on.

Great comment. You could do a similar one for a lot of different fields. Solar panels, windmills, nuclear fusion, medical advances.

> -"...in a simulation":

This position entails climate denialism. Do you?

What is the connection between distrusting effects that have only been observed in models, and disbelieving climate change?

Since you appear to be asking in good faith, despite this being a frankly irrationally hostile environment whenever the subject comes up, I’ll answer.

The raw data shows no warming trend. NOAA and NASA admit this, it’s not a conspiracy theory. The adjustments made that show warming are based on models. Hence to trust the warming trend you have to trust the models, which are very computer simulations.

"In hematite"

Probably could use qualification in the title because it's clickbait as it stands.

Is this basically a naturally occurring Halbach Array?

https://en.wikipedia.org/wiki/Halbach_array

Halbach arrays are non-symmetric but have both poles in equal strength, just not on opposing sides of the array.

These are quasi-particles -- emergent collective behavior of a group of particles.

Discovering true magnetic monopoly would be biggest discovery in physics since ____. Gauss's law of magnetism violated. This was not it.

It is not possible for a group of particles to have a divergent field when none of the individual particles have a divergent field.

This is not less interesting because it's "just a quasi-particle".

This is 2d surface behavior of a solid material. The magnetic fields on the 2d surface act as if there are mobile particles with magnetic charge moving around on the surface.

This is far less interesting for two reasons:

1. No new particles for starters.

2. This is not first time magnetic monopoly quasiparticles have been discovered in materials. Mangetic monopoles have been discovered in materials in the past https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.10..., https://www.nature.com/articles/news.2009.881

If true, I assume there is a quantum of magnetic... "charge"? E.g. something like h_bar*e? (Sorry, I could go away and figure out the correct units here, but I haven't bothered...)

I did my M.SC in one of the High energy physics experiments looking for "natural" magnetic monopole but now moved for supersymmetry then flavor physics.

The title is basically clickbait and personally it triggers a collective truma of hundreds who worked on that during the last 7 decades. Well we might actually have discovered a magnetic monopole in the 80s on the famous valentine's day experiment/incident. [1]

As many people here mentioned, these are not the groundbreaking and fundamental particles that we call magnetic monopole that was predicted by Dirac or GUT monopole (predicted by many grand unification theories). This manifestation of spin effects is consistent with the unsymmetric Maxwell's equations we have and wouldn't prompt a modification like if we discovered the "fundamental" magnetic monopole. Well thanks to inflation, we probably never going to be able to see it even it exists. [2]

Probably titles like these are part of the reason why HEP physicists have their own APS conference (april) and don't participate in the more generic march conference /S.

[1]https://www.nature.com/articles/429010a

[2] https://en.m.wikipedia.org/wiki/Big_Bang#Magnetic_monopoles

Reminds me of how you occasionally get a "GRAD STUDENTS BREAK SPEED OF LIGHT" article and it turns out they just shined a laser on the moon and turned it really fast or something.

Because it's possible to make things (like a laser spot or a shadow) move faster than the speed of light.

It's moving information faster than the speed of light that's tricky.

Is there consensus how actual magnetic monopoles relate to the particles in the Standard Model?

Good question, the short answer is no. For the long answer, let's begin by simplifying the concept of the Standard Model itself.

The Standard Model is a theory that describes the fundamental particles and forces (except gravity) in the universe. It is essentially a set of mathematical equations that explain how particles like quarks and electrons interact through forces mediated by particles like photons (for electromagnetic force), W and Z bosons (for weak nuclear force), and gluons (for strong nuclear force). These interactions are described using quantum field theory, which combines quantum mechanics (dealing with the smallest scales of energy levels and particles) with special relativity (dealing with particles moving at high speeds).

Now, regarding magnetic monopoles, these are hypothetical particles proposed in various theories. There are two main types of hypothetical magnetic monopoles that theorists have considered:

- Dirac Monopoles: Proposed by Dirac in 1929, these monopoles are simpler and would arise from modifications to electromagnetism. Dirac showed that if magnetic monopoles exist, they would explain why electric charge is quantized (i.e., why it comes in discrete amounts like the charge of an electron). However, Dirac monopoles don't fit neatly into the Standard Model as it currently stands. They would require some extension or modification of the model.

- Grand Unified Theory (GUT) Monopoles: These are more complex and emerge from grand unified theories, which are theoretical frameworks that attempt to unify the gravity, electromagnetic, weak, and strong forces into a single force. In these theories, monopoles are heavy and rare relics from the early universe, a time when the fundamental forces were unified. In many GUTs, conditions in the early universe would have allowed for the creation of magnetic monopoles. These monopoles are predicted to be very massive and thus difficult to produce and detect with current technology (LHC energies are still too low to produce them).

So as of now, there is no experimental evidence for magnetic monopoles (this did not change by this announcement). Their theoretical existence is a topic of significant interest, but it remains speculative and outside the direct scope of the Standard Model. Any confirmation of magnetic monopoles would be groundbreaking, potentially opening up new physics beyond the Standard Model.

"Well thanks to inflation."

Probably Biden's fault.

I maintain nonetheless that yin-yang dualism can be overcome. With sufficient enlightenment we can give substance to any distinction: mind without body, north without south, pleasure without pain. Remember, enlightenment is a function of willpower, not of physical strength.

> they found hidden patterns of magnetic charges within hematite, including monopoles, dipoles and quadrupoles.

I appreciate the context on "monopoles" in this thread. Can anyone help me wrap my head around quadrupoles?

The wiki on this topic is not to bad [0].

Essentially, it's a configuration of 2 south poles and 2 north poles. It's pretty important if you're doing quantitative magnetism. Many magnetic configurations don't generate a pure dipole-like field, but also need higher order contributions - like quadrupole and octopole moment - if you want to model/calculate the field.

Quadrupoles also have useful technical properties, you can use one to re-focus the beam in a particle accelerator, for example. In a sense, they act like magnetic lenses.

[0] https://en.wikipedia.org/wiki/Quadrupole

Thanks. I looked at that, but I don't have the maths background to follow the real explanation. I get the four bar magnets or four coils stuck together, as an example of the charge state, but that looks simplified to the point that it's maybe not real. I think I'm trying to bridge a gap in my understanding between "this is a convenient way to refer to a complex interaction between multiple magnetic fields", and "this is a object (constructed? naturally occurring?) that I can hold in my hand".

Or, maybe that's not even a reasonable mental model / distinction - magnetics be freaky.

In a different perspective, the magnetic field itself is a result of special relativity. The magnetic field is an alternative way to explain electromagnetism without citing special relativity. (Or to say, electrostatic field and special relativity are sufficient to explain everything in electromagnetism, the existence of magnetic field is unnecessary.)

If the existence of magnetic field is unnecessary, there is no reason to even search for a magnetic monopole.

Does this imply the existence of field lines which are not loops? (in 3-D)

Create a sphere out of bar magnets.

The interior hollow. The shell comprised of bar magnets with all the PLUS pointed inward and the MINUS pointed outward.

That would be like a MINUS MONOPOLE.

Yes no maybe?