The end of the life of quasiparticles: scientists found how to study this process

Physicists have learned how quasiparticles end their lives

In quantum mechanics, when particles interact in large systems, a special phenomenon arises. It consists in the fact that groups of particles begin to behave like individual particles. Such groups of physics are called quasiparticles. Knowledge of their properties can be an important key to understanding the management of technologically important quantum effects. These include superconductivity and superfluidity.

The scientists believe that quasiparticles are useful only until the moment when they stop their life path. For many quasiparticles, it threshold occurs when they are considered as young, their life lasts only a few moments, lasting less than one second.

The researchers from Moshan University decided to study that unusual process and find out how the quasiparticles die. The main version leads to decay, usually it is the behavior of a low-energy quasiparticle. But that is due to the multiparticle dephasing. It is a disordering of the constituent quasiparticles, and the process occurs by itself, in a natural way over a certain period of time.

As the disorder intensifies, the previously inherent property of a quasiparticle with an ordinary particle also disappears. And in the end, the inevitable effect of multiparticle dephasing destroys the quasiparticle. That effect is negligible.

But the researchers showed that the dephasing of many bodies is capable of dominating other forms of quasiparticle destruction, perceived as the death of a quasiparticle. The researchers conducted an experiment with a particularly "pure" quasiparticle. It consists of an ultracold atomic gas impurity. In that state, they managed to find convincing evidence of multiparticle dephasing.

The same phenomenon was confirmed in previous experimental results. By focusing on that case, the scientists found out that the ultracold atomic gas is the Fermi Sea. The impurity in the Fermi Sea produces a quasiparticle known as a repulsive Fermi polaron. It is a complex quasiparticle, which is extremely difficult to study in theory and in experiments.

The model created by the researchers showed demonstrates the effects of many-particle dephasing in a repulsive Fermi polaron. And the evidence turned out to be more compelling to accept the fact that multiparticle dephasing is fundamental to the nature of quasiparticles.