The basic idea behind quantum mechanics is that you can quantify things, which implies that there is some fundamental unit for different types of particles and energy. For thermal energy, the quantum is the phonon, a quasiparticle representing the vibrations of atoms that possess the same wave-particle duality as photons. This has led some to wonder if a phonon-based laser could be developed, and now researchers at Berkeley Lab have finally shown something that may lead to such a device.
A requirement of a laser-like device is that the quantum involved can achieve coherence. In the typical laser, this means that the peaks and troughs of the many light waves are aligned and do not interfere with each other. Whether phonons could achieve coherence has been debated for some time, but now the answer has been decided by the Berkeley Lab researchers. Using a superlattice with varied interface densities, the researchers were able to show that phonons traveling through it crossed over incoherent particle-like transport to coherent wave-like transport.
Now that we know it is possible for phonons to achieve coherence, researchers can get to work on the developments needed to create a phonon laser. Such a device could be used to improve ultrasound imaging, create highly accurate measuring devices, and more.
Source: Berkeley Lab