Composite fermions and quartets in the Fermi-Bose mixture with attractive interaction between fermions and bosons

TL;DR

This paper explores a Fermi-Bose mixture model with attractive interactions leading to composite fermions and quartets, relevant for high-temperature superconductivity and ultracold atomic experiments.

Contribution

It introduces the concept of composite fermions and quartets forming in a Fermi-Bose mixture with strong inter-species attraction, expanding understanding of pairing mechanisms.

Findings

Composite fermions can form due to fermion-boson pairing.

Quartet formation occurs at low temperatures with equal fermion and boson densities.

The model has implications for high-$T_c$ superconductors and ultracold atomic gases.

Abstract

We consider a model of Fermi-Bose mixture with strong hard-core repulsion between particles of the same sort and attraction between particles of different sorts. In this case, besides the standard anomalous averages of the type $<b>$; $<bb>$ and $<cc>$, a pairing between fermion and boson of the type $bc$ is possible. This pairing corresponds to a creation of composite fermions in the system. At low temperatures and equal densities of fermions and bosons composite fermions are further paired in quartets. Our investigations are important for high-$T_c$ superconductors and in connection with recent observation of weakly bound dimers in magnetic traps at ultralow temperatures.