This groundbreaking discovery about the one-way diffraction of sound waves could pave the way for future communication technologies.
Researchers have uncovered a remarkable phenomenon in the movement of sound waves, which may enhance the development of sophisticated communication devices that utilize acoustic technology. This research was spearheaded by the Institute for Materials Research at Tohoku University, in partnership with the Japan Atomic Energy Agency and the RIKEN Center for Emergent Matter Science.
Surface acoustic waves (SAWs)—the elastic waves that travel along the surfaces of materials, similar to how ripples move across a pond—are fundamental to the communication technologies we use today. These waves are vital components in frequency filters found in everyday gadgets like smartphones, as they convert electrical signals into vibrations or “ripples” using the piezoelectric effect for effective signal management. Therefore, gaining a clearer insight into how SAWs behave is crucial for the progress of future technological advancements.
During their experiment, the researchers employed cutting-edge nanofabrication methods to design a periodic arrangement of nanoscale magnetic materials. This magnetic nanostructure acts like a specialized grating that the sound waves interact with. Surprisingly, rather than the conventional symmetric diffraction pattern, the team discovered an entirely new, asymmetric diffraction behavior of SAWs, termed “nonreciprocal diffraction.”
“This phenomenon had only been observed in the field of optics before,” says Yoichi Nii, “so we’re thrilled to confirm its existence in other wave disciplines as well.”
Through theoretical evaluation, the team found that this unique asymmetry is a result of the distinct interactions between SAWs and the magnetic materials, particularly related to their angular momentum.
This discovery might allow for precise manipulation of SAW pathways using magnetic fields, paving the way for the creation of groundbreaking acoustic devices that could improve both classical and quantum communication technologies. Revealing new characteristics of SAWs is vital for the evolution of next-generation communication systems and equipment.
The findings were published in Physical Review Letters on January 14, 2025.
