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I tell my students that if they can discover a magnetic monopole, then they will receive a Nobel Prize in Physics. An article published recently in Science discusses experiments that seem to have uncovered the elusive magnetic monopole. Why is this important? Why is this news not quite as exciting as you might think?

Maxwell’s Equations are really quite elegant. Four relatively simple equations describe the entirety of electromagnetic phenomena, including light, electric circuits and refrigerator magnets.

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There is a very nice symmetry to these equations. Specifically, if you have no current (J) and no charge (rho), then the equations are remarkably symmetric. Specifically, you can replace E with B and B with . The problem is, though, that this symmetry is obliterated in the presence of an electric current or charge! If the electric field part of things has a J and a Rho, then why in the world doesn’t the magnetic field side? Let’s just assume that there is such a thing as a magnetic “charge” and current. You would end up with:

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Now THAT is a beautiful set of symmetric equations. It is even more beautiful, in that the consequences of simply assuming their existence leads to a nice and tidy explanation of other things, as well, such as the quantization of charge. Dirac showed that to be the case.

There is a small problem, though. No one has ever found a reproducible magnetic “charge” or current. That kind of throws cold water on our little thought exercise. Well, in September the news broke: we have found the elusive magnetic monopole!

Both studies examine the magnetic behavior of a family of rare-earth materials known as spin ices—one group using holmium titanate and the other dysprosium titanate. The man-made spin ices take their name from their similarity to water ice—at the molecular level their internal magnetic structure is analogous to the arrangement of protons in ice.

Claudio Castelnovo, a postdoctoral physicist at the University of Oxford who co-authored one of the Science papers and also co-wrote a paper in Nature last year describing how monopoles might be realized in spin ices, explains that the compounds offer a peculiar combination of order and freedom that facilitates the dissociation of the poles.

Make no mistake, this is hella exciting. However, let me add some cold water to these spin ices (ha ha!). It turns out that these “monopoles” are actually only quasi-particles. The divergence of B (MW 2) is still zero everywhere in these systems, which means that they are not TRUE monopoles. They just act like them.

String theorists want magnetic monopoles to exist. They must if their theory is going to cut it, since if they don’t exist, then the rug will be pulled right out from under the theory. These new discoveries are pretty awesome, especially for someone in a condensed matter field. However, they don’t seem to help our theorist friends that much, and they don’t yet validate our dead friend Dirac.