Researchers defy 19th Century law of Physics in 21st-century boost for energy efficiency

The coupling between two magnetic elements can be made extremely asymmetrical.


Scientists at the University of Sussex have transformed a 156-year-old law of physics on its head in a development that could prompt more productive recharging of batteries in cars and cell phones.

Scientists, for the first time, have exhibited that the coupling between two magnetic components can be made amazingly asymmetrical.

In collaboration with the Austrian Academy of Sciences and the University of Innsbruck, scientists rip up the physics rulebook by demonstrating that it is conceivable to influence one magnet to interface with another without the connection happening in the other direction.

However, the study runs in opposition to long-established beliefs of magnetic coupling, which rise up out of the four Maxwell conditions going back to the seminal works of Michael Faraday and James Clerk Maxwell in the nineteenth century.

Dr Jordi Prat-Camps with the model of his experiment Credit: University of Sussex
Dr Jordi Prat-Camps with the model of his experiment Credit: University of Sussex

Dr. Jordi Prat-Camps, a research fellow at the University of Sussex, said: “We have created the first device that behaves like a diode for magnetic fields. Electric diodes are so crucial that none of the existing electronic technologies such as microchips, computers or mobile phones would be possible without them.”

If our result for magnetic fields would have one millionth of the same impact as the developments in electric diodes, it would be a hugely impactful success. The creation of such a diode opens up a lot of new possibilities for other scientists and technicians to explore.”

“Thanks to our discovery we think it might be possible to improve and the performance of wireless power transfer technologies to improve the efficiency of recharging phones, laptops and even cars.”

For the study, scientists focused on the control and manipulation of magnetic fields by the use of metamaterials. By studying the mechanism, scientists have developed a new tool to control magnetism including attractive undetectability cloaks, magnetic concentrators, and wormholes.

By solving Maxwell’s equations analytically, the researchers very quickly demonstrated that not only could reciprocity be broken down but that, the coupling could be made maximally asymmetric, whereby the coupling from A to B would be different from zero, but from B to A it would be exactly zero. Having shown that total unidirectional coupling was possible theoretically, the team designed and built a proof-of-concept experiment that confirmed their findings.

Dr. Prat-Camps said: “The magnetic coupling between magnets or circuits is extremely well-known. It dates back to the seminal works of Faraday and Maxwell, and it is deeply embedded into the four Maxwell equations that describe all electromagnetic phenomena. A vast majority of the technologies we rely on today are based on magnetic coupling, including motors, transformers, low-frequency antennas, and wireless power transfer devices. As far as we know, nobody before us thought to ask whether this symmetry could be broken and to what extent.”

Scientists expect that the study could have wide implications.

Innsbruck physicists Oriol Romero-Isart and Gerhard Kirchmair said: “If the coupling between coils is symmetric, some part of the energy can also flow in the opposite direction which can greatly reduce the efficiency of the transfer. By using a magnetic diode to prevent this backward flow, the efficiency of the transfer could be greatly enhanced.”

The study is published in the journal Physical Review Letters.


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