Physics

Synthetic magnetic monopoles have been created in the lab

January 31, 2014 | by Lisa Winter

Photo credit: Heikka Valja

A magnet always has a north and a south pole. Even if a magnet is cut in half down to the atomic level, magnetic fields are bipolar. However, in 1931 it was theorized that there are natural monopoles which help explain some of the peculiarities of magnetism. This has never before been tested because scientists have not been able to create monopole elementary particles in the lab that could be studied individually - until now.  The research was led by David Hall of Amherst College and the results were published in Nature.

Hall’s lab was able to create the monopole particles by chilling rubidium atoms to less than 100-billionths of a degree warmer than absolute zero. This temperature drives atoms into a Bose-Einstein condensate (BEC), which is the lowest quantum state possible. This condensation causes the rubidium to act differently than they normally would, forming a cloud that acted like a wave and not a group of individual particles. The cloud was then induced into a vortex to align all of the particles to the same magnetic orientation. A single rubidium atom was placed in the middle of the vortex, it created a hole in the center, completely void of atoms, creating the monopole atoms.

For the first time, physicists will be able to test the theories laid out by Paul Dirac 83 years ago. The monopole particles created in this experiment are structurally identical to those that he theorized. Dirac suspected that monopole elementary particles would be compatible with the Standard Model and could explain why the charges of protons and electrons act like discrete units, which seem to create an imbalance of electrostatic charges as they attract and repel one another.

Just because these monopole particles have been created in the lab does not necessarily mean that they exist in nature, but if they do, researchers will now have a better idea of what to look for. Popular targets for these are rocks and samples from the moon. If natural monopoles do exist, they were likely formed shortly after the Big Bang, as the conditions were much more energetically favorable than they are now. This is still a tremendous accomplishment, because it gives evidence that natural monopole particles like Dirac theorized are actually possible. 

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