Ultracold Quantum Device Generates Sound-Like Particles

Researchers at McGill University have developed a new device that creates sound-like particles called phonons at extremely cold temperatures. This technology could lead to the development of phonon lasers. These lasers may have applications in communications and medical diagnostics.

The device operates by passing an electrical current through a two-dimensional crystal layer. This process traps electrons in a channel that is only a few atoms thick. When electrons are driven through this channel with sufficient force, they release energy as bursts of phonons. These bursts occur in predictable and tunable patterns.

Cooling the devices to temperatures between ten milli-Kelvin and 3.9 Kelvin enables this process. At these ultracold temperatures, electrons behave more predictably. This allows for the observation of quantum effects, where matter exhibits wave-like properties.

Michael Hilke, an Associate Professor of Physics and co-author of the study, noted that at absolute zero temperatures, sound is only created when electrons travel collectively at or above the speed of sound. Earlier research observed similar effects as electron speeds approached the sound barrier. This new study pushes the system beyond that point. It indicates that existing theories may need revision to account for electrons being very hot even when the host crystal is near absolute zero.

The research was published in *Physical Review Letters*. The device was constructed and analyzed at McGill and the National Research Council of Canada. The material used in the device was synthesized at Princeton University.

The next phase of research will explore using other materials, such as graphene, to accelerate the device's operation. This advancement could lead to high-speed communication technologies, advanced sensing tools, and improved medical systems.