Innsbruck quantum physicists have developed a diode for magnetic fields and then tested it in the laboratory. The device, built by the research groups led by the theorist Oriol Romero-Isart and the experimental physicist Gerhard Kirchmair, could pave the way for a number of new applications.
Sketch of the unidirectional magnetic coupling between two coils placed near a moving conductor. When the left coil is energized, the magnetic field reaches the right coil (top). When the right coil is energized, the magnetic field does not reach the left one (bottom). (Credit: Luis Veloso)
Electric diodes are vital electronic components that conduct electricity in one direction but stop conduction in the opposite one. They are located at the core of any electronic component, being one of the most crucial building blocks. Thus far there were no such components for magnetic fields. Physicists at the University of Innsbruck and the ÖAW Institute of Quantum Optics and Quantum Information (IQOQI) are now altering that. They engineered the first diode for magnetic fields and displayed its functionality in the laboratory.
“Our device makes possible to transfer the magnetic field from a first magnetic element—for example, a magnet or a coil—to a second one. When roles are inverted and one tries to send magnetic field from the second to the first, no magnetic field is transferred,” explains first author Jordi Prat Camps, who is currently a researcher at the University of Sussex in England. In technical terms, this means that the shared inductances between the two sources, which are usually expected to be symmetric, can be made very asymmetric. The main element to attain this result is the use of an electrical conductor that moves with constant velocity.
When the conductor is properly placed near to the magnetic elements and is moved at the right speed, the coupling between them becomes unidirectional, and a diode for magnetic fields is realized.
Jordi Prat Camps, Researcher, University of Sussex.
Coupled magnetic elements are used in many major technologies like transformers, electric motors, magnetic memories or MRI machines. The magnetic elements are symmetrically coupled in all of them
. “The availability of a new magnetic tool like a diode might thus open a bunch of new possibilities”, Gerhard Kirchmair points to the future. For instance, the efficiency of wireless charging devices could be enhanced, since the energy can only travel from the charging station to the device and not in the opposite direction.
The research was funded by the Austrian Ministry of Education, Science and Research and the European Union and reported in the journal
Physical Review Letters.