💥 After photon lasers, here come phonon lasers

A research team at McGill University has developed a novel device that, at extremely low temperatures, generates particles similar to sound waves: phonons. This technology could be used to create phonon lasers and have applications in communications and medical diagnostics.

"Modern communications rely heavily on light, including electromagnetic waves and electric currents. However, sound can travel in certain environments where light and electric currents cannot, such as the oceans," explains Michael Hilke, associate professor of physics and co-author of the study. "Sound waves can also have practical applications inside the human body."


The device was built and analyzed at McGill University and the National Research Council of Canada (NRC). The material was synthesized at Princeton University.

Fast electrons produce vibrations similar to sound vibrations. The device passes an electric current through a two-dimensional crystal layer and traps electrons in a channel located in an area only a few atoms thick. The scientists discovered that when the electrons were pushed with sufficient force through this channel, they released energy in the form of vibration waves akin to sound vibrations — phonons — in predictable and tunable patterns.

To achieve this effect, they must cool the device to temperatures between about 10 millikelvins and 3.9 kelvins, to make electron behavior more predictable and allow observation of quantum effects, which occur when matter behaves like waves rather than solid particles.

"At zero temperature — that is, in the quantum physics universe — no sound occurs unless electrons move together at or above the speed of sound," says Michael Hilke. "Previous studies have observed related effects when electrons moved at speeds close to the speed of sound." "We push the system well beyond this point and show that existing theories need to be reassessed to account for the fact that electrons can be very hot, even though the host crystal temperature is near absolute zero."

New materials could accelerate speed. Michael Hilke notes that the next step will be to investigate other fabrication materials, such as graphene, to further accelerate the device's operation.

This acceleration could pave the way for high-speed communications technology, as well as the development of detection tools, biological materials, and advanced medical systems.

"Phonons are difficult to generate and control; that's why we are exploring new schemes." "More broadly, we seek to understand the flow and conversion of electric current and energy inside advanced electronic materials," he adds.

The study: The article "Resonant magnetophonon emission by supersonic electrons in ultrahigh-mobility two-dimensional systems," by Michael Hilke et al., was published in the journal Physical Review Letters.