For the first time, scientists have succeeded in cooling a sound wave in a silicon tube. And infrared radiation helped them in this.
A team of physicists led by Niels Otterstrom cooled free phonons - quasiparticles that reflect the nature of atomic vibrations in a solid. They managed to achieve a temperature drop of 30 degrees Celsius.
This is the first time that scientists have been able to cool a sound wave in practice. Prior to this, a similar procedure was performed using optomechanical cavities, which limits the use of laser cooling. By cooling phonons directly, one can obtain the so-called squeezed quantum states, which are used to detect gravitational waves.
To achieve this result, physicists took a long time to select the necessary wave configuration, which would ensure the maximum interaction between laser photons and phonons in a sound wave. Scientists have also developed a detailed model of the sound wave and theoretically substantiated the process of its cooling.