This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Every time someone picks up a call, the phone does a quiet bit of translation. Incoming radio signals are converted into tiny sound waves that ripple across chips before being turned back into data.
"Those waves are useful but unruly," says physicist A.T. Charlie Johnson of the School of Arts and Sciences. Imperfections in the material, he explains, can bounce waves backward or send them off course, and every stray reflection hampers the signal.
Now, researchers led by Johnson with collaborators at the University of Texas at Austin have developed a device that keeps those waves on track. Their findings are published in Physical Review Applied. Penn Today spoke with Johnson about this work, which could pave the way for next-generation communications devices and signal processing.
About two decades ago, Penn theoretical physicists Charles Kane and Eugene Mele showed how topology—the mathematics of properties that survive stretching and bending—governs how electrons move through certain materials. They used this to predict the quantum spin Hall effect, a phenomenon that explains how electrons travel along a material's edge. "Charlie and Gene were thinking about quantum waves—electrons in materials," Johnson says.
"But the same ideas hold for light waves, and they also hold for sound waves, which is what we're working with." The chip is made from aluminum nitride, a material already used in cell phone components and compatible with standard chipmaking. But this chip has a special pattern etched into it—a lattice of tiny star shapes arranged one way on one side of a boundary and another way on the other side. The wave always travels with one pattern on its right and the other on its left.
To reverse, it would have to flip that arrangement, which takes a dramatic disruption. "The design forces the wave to travel along the interface between the two," Johnson says. "It can't go into one side, and it can't go into the other." In tests, the waves rounded sharp 120-degree corners of a zigzag path without scattering.
Extract — continue reading at the source.
