Topping the looooong list of things I would give a full ResearchBlogging write-up if I had time is this new paper on a ultra-cold atom realization of “Dirac Monopoles”. This is really cool stuff, but there are a lot of intricacies that I don’t fully understand, so writing it up isn’t a simple matter.
The really short version, though, is that a team of AMO physicists have created particles that are analogous to magnetic monopoles– that is, to a particle that was only a “north” or “south” pole of a magnet, not both together like a conventional bar magnet (leading to my favorite social-media reshare text for a story about this, from Davin Flateau on Facebook: “Take that, del dot B equals zero”). These get Dirac’s name appended because he wrote a famous paper showing that if magnetic monopoles exist somewhere in the universe, that would explain the quantization of electric charge– why every particle we know of has a charge that is some simple multiple of the electron charge. Of course, we haven’t had much luck finding any, and particle cosmologists now think there may be only a handful of them within the visible universe– in fact, inflationary cosmology was invented in part to explain the fact that we haven’t seen any magnetic monopoles.
Lacking naturally occurring monopoles, of course, physicists set out to create something that looks like them. Which leads to the current experiment, through a long chain of “likes.” That is, magnetic fields are generally produced by electric currents, so a particle with magnetic properties is in some sense like a tiny loop of current. And loops of current are made up of lots of charged particles running around in a circle, so a bunch of neutral particles running in a circle is in some sense like a loop of current. And you can make vortices in superfluid helium that are just like the little loops of current you get in a superconductor, and a Bose-Einstein Condensate (BEC) of rubidium atoms is just like a sample of superfluid helium.
So, what these guys did was to create vortices in their BEC of rubidium, which behave just like current loops, which are like magnetic particles. And if you tweak the parameters of the BEC around in just the right way, you can set up a situation in which these vortices interact with their environment in exactly the way that magnetic monopoles should. This is one “like” away from some previous experiments that did this inside a superconductor, but has the usual advantages of working with dilute ultra-cold-atom systems, namely that you can easily adjust the parameters “on the fly,” without needing to make entirely new material samples. This lets them produce beautifully clear illustrations of the properties they’re looking for. It’s a spectacular experiment.
(You can get a bit more detail about the underlying physics in Matthew Francis’s write-up for Ars Technica, which is pretty good.)
Of course, since everything on this blog is ultimately about me, the really important thing here is not that this is an awesomely cool demonstration of some really neat physics– though it is all that– but that it plays into one of my particular obsessions about academia. These experiments were not done at NIST, or Harvard, or the Max Planck Institute, but in Dave Hall’s lab at Amherst College. Two of the authors are at a university in Finland, but they’re the theorists who came up with the scheme. The actual execution of the experiment, and the taking and analyzing of the very impressive data, was done by a faculty member and two students (possibly one student and a post-doc, but I think the one who’s moved on was a student who graduated) at an institution with under 2,000 students and no graduate program.
Which is a rebuke of sorts to people who continue to insist that the only true meaning of success in academia is landing a tenured position at a major research university. In fact, people can and do carry on outstanding research programs even at small colleges. By choice– Dave’s an Amherst grad, and I’m pretty sure he went after that job specifically, not as a fall-back position when Caltech didn’t come calling.
(Of course, the next step is “Well, Amherst is special, and they have more money than some research institutions, so they’re not really a small college…” And you can ride that road all the way to the land of the true Scotsmen if you like.)
So, as much as it pains me as a Williams guy to praise those filthy defectors who stole our library in 1821*, as a small-college guy, I’m particularly excited to see such a great result come from a small college lab. This is great stuff, both in terms of physics and on the meta level of academic politics. It also doesn’t hurt that Dave is a terrifically nice guy (and I’m not just saying that because he was an external reviewer on my tenure case, either…).
(*- Yes, I know that the library theft is a rural legend (PDF). It’s part of the Little Three atmosphere, though, and can’t be dumped that easily.)