Researchers from the UK's University of Cambridge say they have unraveled one of the mysteries of electromagnetism, a breakthrough that could enable the design of antennas small enough to be integrated into an electronic chip. The development could have implications for the Internet of Things (IoT).
In new results published in the journal Physical Review Letters, the researchers propose that electromagnetic waves are generated not only from the acceleration of electrons but also from a phenomenon known as symmetry breaking.
The researchers explain that in physics, symmetry is an indication of a constant feature of a particular aspect in a given system. When electronic charges are not in motion, there is symmetry of the electric field.
Working with researchers from the National Physical Laboratory and Cambridge-based dielectric-antenna company Antenova, the Cambridge team used thin films of piezoelectric materials, a type of insulator that is deformed or vibrated when voltage is applied. At a certain frequency, these materials become not only efficient resonators but also efficient radiators, so they can be used as antennas, according to the university.
"Antennas, or aerials, are one of the limiting factors when trying to make smaller and smaller systems, since below a certain size, the losses become too great," said Professor Gehan Amaratunga of Cambridge's Department of Engineering, who led the research, in a university news post. "An aerial's size is determined by the wavelength associated with the transmission frequency of the application, and in most cases it's a matter of finding a compromise between aerial size and the characteristics required for that application."
The researchers found that by subjecting the piezoelectric thin films to an asymmetric excitation, the symmetry of the system is similarly broken, resulting in a corresponding symmetry-breaking of the electric field and the generation of electromagnetic radiation.
"If you want to use these materials to transmit energy, you have to break the symmetry as well as have accelerating electrons--this is the missing piece of the puzzle of electromagnetic theory," Amaratunga said. "I'm not suggesting we've come up with some grand unified theory, but these results will aid understanding of how electromagnetism and quantum mechanics cross over and join up. It opens up a whole set of possibilities to explore."
Piezoelectric materials can be made in thin film forms using materials such as lithium niobate, gallium nitride and gallium arsenide. Gallium arsenide-based amplifiers and filters are already available on the market, and this new discovery opens up new ways of integrating antennas on a chip along with other components, according to the university.
Symmetry breaking also can be applied in cases such as a pair of parallel wires in which electrons can be accelerated by applying an oscillating electric field. "In aerials, the symmetry of the electric field is broken 'explicitly' which leads to a pattern of electric field lines radiating out from a transmitter, such as a two wire system in which the parallel geometry is 'broken,'" said Dhiraj Sinha, the paper's lead author.
"It's actually a very simple thing, when you boil it down," Sinha said. "We've achieved a real application breakthrough, having gained an understanding of how these devices work."
The research is supported in part by the Nokia Research Center, the Cambridge Commonwealth Trust and the Wingate Foundation. The East of England Development Agency, Cambridge University Entrepreneurs and Cambridge Angels provided support as well.
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