August 9, 2022

Topological phenomena found at high frequencies

Topological phenomena found at high frequencies

A new study has demonstrated topological control capabilities in an acoustic system, with implications for applications such as 5G communications and quantum information processing.

This research builds on concepts from the field of topological materials, a theoretical framework developed by Penn’s Charlie Kane and Eugene Mele. One example of this type of material is a topological insulator, which acts as an electrical insulator on the inside but has a surface that conducts electricity. Topological phenomena are hypothesized to occur in a wide range of materials, including those that use light or sound waves instead of electricity.

In this study, the main researcher was interested in studying topological phononic crystals, metamaterials that use acoustic waves, or phonons. In these crystals, topological properties are known to exist at low frequencies in the megahertz range, but he wanted to see if topological phenomena might also occur at higher frequencies in the gigahertz range because of the importance of these frequencies for telecommunication applications such as 5G.

To study this complex system, the researchers combined state-of-the-art methodologies and expertise across theory, simulation, nanofabrication, and experimental measurements. First, researchers conducted simulations to determine the best types of devices to fabricate. Then, based on the results of the simulations and using high-precision tools, the team etched nanoscale circuits onto aluminum nitride membranes. These devices were then shipped to a lab for microwave impedance microscopy, a method that captures high-resolution images of the acoustic waves at incredibly small scales.

The key finding of this work is the experimental evidence showing that topological phenomena do in fact occur at higher frequency ranges. Another important result is that these properties can be built into the atomic structure of the device so that different areas of the material can propagate signals in unique ways. (SciTechDaily)

The work has been published in Nature Electronics.

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