Led by David Hall of Amherst College, an international team of physicists has created, identified, and photographed an isolated north pole (a monopole) in a simulated magnetic field.
Artist’s depiction of a magnetic monopole.
“The creation of a synthetic magnetic monopole should provide us with unprecedented insight into aspects of the natural magnetic monopole — if indeed it exists,” Hall said, explaining the impact of his group’s discovery.
Typically speaking, magnetic poles come in pairs – a north pole is always tied with a south pole. What’s interesting is that if you were to take, say, a magnetic bar, and cut it in half, you would not wind up with an individual north pole and an individual south pole, but rather two separate magnets, each equipped with their own north and south poles. Their electrostatic cousins, however — positive and negative charges — are able to exist independent from one another.
This raises one pretty big question: do magnetic monopoles actually exist? That is, can a magnetic north pole exist without a south pole, and vice versa? In 1931, following a series of experiments, British physicist Paul Dirac confirmed it is possible, but only in the context of quantum mechanics. Despite his findings, though, decades of subsequent research, in which scientists studied everything from moon rock to fossilized mineral, there was not a single discovery of any natural-occurring magnetic monopoles.
Which brings us to today, and the creation of an actual magnetic monopole.
There were two instances that led to Hall taking on this endeavor: a group meeting in 2011 with Amherst summer student researchers opened the door to the idea of creating a magnetic monopole, whereupon during the research stages they came across a paper published in Physical Review letter Letters in 2009 by researchers Ville Pietilä and Mikko Möttönen, now at Aalto University in Finland, which raised some pretty interesting theories on the matter.
Their paper suggests following a particular sequence of changing external magnetic fields could lead to the creation of a synthetic monopole.
Specifically, they explored how an electron would behave in the vicinity of a magnetic monopole using a gas of approximately one million rubidium atoms, cooled to less than 100-billionths of a degree above absolute zero, because at this point, the atoms begin to lose their individual identities and instead become part of a collective quantum state of matter known as a Bose-Einstein condensate.
Upon reading through the paper, Hall decided he had to contact them and take on this project.
“It felt as though Pietilä and Möttönen had written their letter with our apparatus in mind,” he said, “so it was natural to write them with our questions. Were it not for the initial curiosity on the part of the students we would never have embarked on this project.”
An atomic refrigerator was built by Hall and his students in the basement laboratory of the Merrill Science Center. As is often the case with experiments, there were several technical hurdles to clear, but for all of their efforts, the team was eventually rewarded with photographs confirming the monopoles’ presence at the ends of tiny quantum whirlpools within the super-cold gas.
Hall reflected on the excitement of this discovery, saying “It's not every day that you get to poke and prod the analog of an elusive fundamental particle under highly controlled conditions in the lab.”
The impact of this discovery will be far and wide. As Hall explains, the creation of synthetic electric and magnetic fields is a fast growing field of physics; one that could lead to the development and subsequent understanding of entirely new materials. He added that the team’s discovery also provides a stronger foundation for the ongoing search for magnetic monopoles at the Large Hadron Collider at CERN.
Möttönen concludes, “Our achievement opens up amazing avenues for quantum research. In the future, we want to get even a more complete correspondence with the natural magnetic monopole.”
Story: phys.org
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