Scientists have suspected that the universe contains magnetic monopoles, yet they are hard to find. For almost a century, the search for magnetic monopoles has been the focus of condensed matter physics.
(Photo : Wikimedia Commons/ National Institute of Standards and Technology)
What are Magnetic Monopoles?
Magnetic monopole refers to a hypothetical fundamental particle which carries only one magnetic pole. This would have a new north or south magnetic charge.
When a bar magnet is split into two, the new pieces usually form new poles and exhibit magnetic field lines the same way as before. In classical physics, it is almost impossible to actually produce a magnetic monopole. With the revolution of quantum mechanics in the early 20th century, experts have begun to unravel the long-established theory.
English physicist Paul Dirac proposed the existence of magnetic monopoles. He believed that their presence was consistent with quantum mechanics and that a single magnetic monopole could explain otherwise inexplicable behaviors of charge. He also suggested that the smallest possible magnetic charge was 68.5 times the charge on an electron, and all larger monopoles should be multiples of it.
Almost a century after Dirac first theorized the existence of magnetic monopoles, scientists still haven't found these materials in the observable universe. The search for this hypothetical object has led some physicists to look for different exploratory paths to find electromagnetic phenomena that seem to act like monopoles. In other words, they are searching for some kind of virtual magnetic monopoles.
Search for an Unusual Phenomenon
In a recent study, experts from the the National University of Singapore, University of Oxford, and University of Cambridge captured the first naturally occurring magnetic monopoles. These materials emerge from collective electron behavior demonstrated by flecks of a type of rust known as hematite. The result of their study is discussed in the paper "Revealing emergent magnetic charge in an antiferromagnet with diamond quantum magnetometry."
According to Hariom Jani from the University of Oxford, these monopoles are a collective state of many spins which twirl around a singularity instead of a single fixed particle. As a result, they emerge through many-body interactions, leading to tiny, localized stable particles with diverging magnetic fields that come out of them.
The discovery of the new class of magnetic monopole can be attributed to two concepts. The first involves the idea of "emergence," first popularized by Nobel laureate Philip Anderson in 1972. In the essay entitled "More Is Different", Anderson explains that in condensed matter physics, the sum of individual physical pieces can exhibit different properties from its parts.
The second concept involves the study of antiferromagnets with diamond quantum magnetometry. This technique enables the examination of the spin of a single electron on the tip of a diamond needle which allows measurement of its magnetic field as its impacts hematite. This method pulls this off without affecting the behavior of the electron.
According to Anthony Tan, it has always been a challenge to directly image the textures in antiferromagnets because of their weaker magnetic pull. With a nice combination of diamonds and rust, they are now able to do so.
Using the two techniques, the team found the hidden patterns of magnetic charges which included expected dipoles and quadrupoles, as well as monopoles. The discovery does not only solve the quantum challenge of whether a magnet's pole can be separated. It could also lead to the development of next-gen storage techniques called racetrack memory or ultra-efficient computing devices.
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