Bose-Einstein condensation of diquark molecules in three-flavor quark matter

TL;DR

This paper investigates the phase diagram of three-flavor quark matter, revealing a transition from loosely bound Cooper pairs to tightly bound diquark molecules and exploring the conditions for their Bose-Einstein condensation.

Contribution

It introduces a detailed analysis of diquark molecule formation and BEC in three-flavor quark matter using an NJL-type model, highlighting the conditions for molecular stability and condensation.

Findings

Diquark molecules are stable at low density and temperature.

Molecular dissociation occurs near the chiral transition temperature (~170 MeV).

Bose-Einstein condensation of molecules requires unrealistically strong attraction.

Abstract

We study the phase diagram of strongly interacting matter with three quark flavors at low and intermediate densities and non-zero temperatures in the framework of an NJL-type model with four-point interactions. At large densities, when the interactions are weak due to asymptotic freedom, quarks form loosely bound Cooper pairs. However, when the density decreases, interactions become stronger and quark Cooper pairs transform smoothly into tightly bound diquark molecules. We find that such molecules are stable at low density and temperature and that they dissociate above a temperature $T_{\rm diss}$ of the order of the chiral phase transition temperature $T_c \sim 170$ MeV. We also explore the conditions under which these molecules undergo Bose-Einstein condensation (BEC). We find that BEC is only possible if we increase the attractive interaction in the diquark channel to (probably unrealistically) large values.