Scientists observe 'quasiparticles' in classical systems for the first time - Phys.org

The idea of quasiparticles was introduced by the Soviet physicist Lev Landau in 1941, and ever since has been highly fruitful in quantum matter research.

But so far, the observation and use of quasiparticles have been limited to quantum physics: in classical condensed matter, the collision rate is typically much too high to allow long-lived particle-like excitations.

This is because the hydrodynamic interaction breaks Newton's third law, which states that the forces between two particles must be equal in magnitude and opposite in direction.

This hypothesis was proven right when the researchers simulated a large two-dimensional crystal made of thousands of particles and examined its motion.

"The work is a first-of-its-kind demonstration that fundamental quantum matter concepts—particularly quasiparticles and flat bands—can help us understand the many-body physics of classical dissipative systems," explains Tsvi Tlusty, one of the corresponding authors of the paper.

"Altogether, these findings suggest that other emergent collective phenomena that have been so far measured only in quantum systems may be revealed in a variety of classical dissipative settings, such as active and living matter," says Hyuk Kyu Pak, one of the corresponding authors of the paper.