Ground state of two-component degenerate fermionic gases

TL;DR

This paper investigates the ground state properties of two-component ultracold fermionic gases, revealing phase transitions driven by interspecies interactions, including expulsion of components and formation of Cooper pairs.

Contribution

It provides a theoretical analysis of how interspecies interactions influence the ground state structure of two-component fermionic gases, highlighting critical interaction strengths for phase changes.

Findings

Repulsive interactions can cause one component to be expelled from the trap center.

Strong attractive interactions lead to the formation of Cooper pairs.

The system exhibits distinct structural phases depending on the sign and strength of interspecies interactions.

Abstract

We analyze the ground state of the two--component gas of trapped ultracold fermionic atoms. We neglect the forces between atoms in the same hyperfine state (the same component). For the case when the forces between distinguishable atoms (i.e., atoms in different hyperfine states) are repulsive (positive mutual scattering length), we find the existence of critical interaction strength above which one atomic fraction expels the other from the center of the trap. When atoms from different components attract each other (negative mutual scattering length) the ground state of the system dramatically changes its structure for strong enough attraction -- the Cooper pairs built of atoms in different hyperfine states appear.