A team of researchers from McGill University and the National Research Council of Canada has developed a device that generates phonons—quanta of sound energy—at temperatures between 10 milli-Kelvin and 3.9 Kelvin.
Technical Achievement
The device operates by sending an electrical current through a two-dimensional crystal layer. This process traps electrons in a channel with a thickness of a few atoms. When the electrons are accelerated past the speed of sound within the material, they release energy in the form of phonons. The study found that the resulting phonons are produced in predictable and tunable patterns.
The material used to construct the device was synthesized at Princeton University. The device was built and analyzed at McGill University and the National Research Council of Canada.
Study Findings and Next Steps
"At absolute zero temperatures, no sound is created unless electrons travel collectively at or above the speed of sound."
The lead author, Michael Hilke, Associate Professor of Physics at McGill University, stated that at absolute zero temperatures, no sound is created unless electrons travel collectively at or above the speed of sound. The study found that electrons can remain hot even when the host crystal is at a temperature near absolute zero, indicating that this effect pushes the system "well beyond" the previously understood threshold. Hilke added that "existing theories need to be reassessed."
The next phase of research includes testing other materials, such as graphene, with the goal of increasing the device's operational speed.
Applications
Potential applications for this technology include:
- Phonon lasers for high-speed communications
- Sensing tools for various environments
- Biological materials analysis
- Advanced medical diagnostics
Hilke noted that sound waves can be a useful tool in media such as oceans and the human body, where light and electrical currents cannot travel effectively.
Funding and Publication
The study was published in the journal Physical Review Letters. It was funded by the Natural Sciences and Engineering Research Council of Canada (NSERC) and the Fonds de recherche du Québec – Nature et technologie (FRQNT).