Researchers develop new quantum device that turns electricity into sound at nanoscale: Here's how

McGill University's researchers have developed a device that generates sound-like particles at extremely cold temperatures. This particle, also known as ‘phonons’, can be used to create phonon lasers, with possible applications in communications and medical diagnostics.

"Modern communication is largely based on light, including electromagnetic waves and electrical currents. In a medium such as oceans, sound can travel, whereas light and electrical currents cannot," said Michael Hilke. "In the human body, sound waves can also be a useful tool," he added.

Michael Hilke, an Associate Professor of Physics and co-author of the study published in Physical Review Letters. The study revealed that the device was built and analysed at McGill and the National Research Council of Canada, and the material was synthesised at Princeton University.

Two-dimensional layer of a crystal

The device sends an electrical current through a two-dimensional layer of crystal and holds electrons within an area just a few atoms thick. The researchers have discovered that when electrons are thrust hard enough using this channel, they release in the form of energy because of bursts of sound-like vibrations, also called phonons, in predictable and tunable patterns.

This is achieved by cooling the devices to extremely low temperatures, ranging from around 10 milli-Kelvin to 3.9 Kelvin, causing electrons to behave in a more controlled and predictable way. Under such conditions, scientists can observe quantum effects, where matter exhibits wave-like properties instead of acting purely as solid particles.

"At absolute zero temperatures, that is, the world of quantum physics, no sound is created unless electrons travel collectively at the speed of sound or above," Hilke explained. "Earlier work had observed related effects as electron speeds approached the sound barrier. Our study goes further by pushing the system well beyond that point and showing that existing theories need to be reassessed by considering that electrons can be very hot even if the host crystal is close to absolute zero temperature," he added.

Hilke noted that the next phase involves testing the device with alternative materials such as graphene, which could enable it to function at even higher speeds. This advancement may pave the way for faster communication technologies, improved sensing devices, applications in biological research, and more sophisticated medical systems. "Phonons are hard to generate and harness in a controlled way, so we are exploring new regimes. At a broad level, this is about how electrical current and energy move and are converted inside advanced electronic materials," he said.