Three-body interactions in Fermi systems

TL;DR

This paper demonstrates that three-body quasiparticle interactions in Fermi systems are significantly suppressed relative to two-body interactions at low energies, with implications for understanding complex many-body phenomena.

Contribution

It provides a quantitative analysis of the suppression of three-quasiparticle interactions in Fermi systems and illustrates this with examples from ultracold gases and nuclear physics.

Findings

Three-quasiparticle interactions are suppressed by the ratio n_q/n or N_q/N.

Suppression is significant at low energies and temperatures.

Examples include polarons in Fermi gases and neutrons in calcium isotopes.

Abstract

We show that the contributions of three-quasiparticle interactions to normal Fermi systems at low energies and temperatures are suppressed by n_q/n compared to two-body interactions, where n_q is the density of excited or added quasiparticles and n is the ground-state density. For finite Fermi systems, three-quasiparticle contributions are suppressed by the corresponding ratio of particle numbers N_q/N. This is illustrated for polarons in strongly interacting spin-polarized Fermi gases and for valence neutrons in neutron-rich calcium isotopes.