Unbalanced droplets of one-dimensional mixtures of fermions

TL;DR

This study uses diffusion Monte Carlo simulations to explore the stability of unbalanced one-dimensional fermionic mixtures of ytterbium isotopes, revealing that slightly unbalanced compositions favor self-bound droplet formation.

Contribution

It demonstrates the existence and stability conditions of self-bound droplets in unbalanced fermionic mixtures, extending previous balanced mixture studies.

Findings

Self-bound droplets are possible in unbalanced mixtures.

Most stable clusters have a slight excess of $^{171}$Yb atoms.

Clusters with excess $^{173}$Yb atoms are only stable in narrow conditions.

Abstract

By means of a diffusion Monte Carlo technique, we study one-dimensional unbalanced mixtures of fermionic Ytterbium atoms ($^{173}$Yb, $^{171}$Yb). This means clusters in which the total number of $^{173}$Yb particles is different from the sum of all the atoms belonging to the $^{171}$Yb isotope. Our aim will be to check the possibility of having self-bound arrangements beyond the balanced compositions reported in previous literature rather than exploring all the situations in which that could be possible. In that vein, we focused mainly on mixtures in which the atoms belonging to one isotope are spin-polarized, while the spins of the particles in the other isotope are evenly distributed in two sets. What we found was that, even tough self-bound droplets are possible for different compositions, the most stable ones are clusters with a slight excess of attractively interacting $^{171}$Yb particles with different spins with respect to the number of spin-polarized $^{173}$Yb atoms. Clusters in which the number of repulsively interacting unequal-spin $^{173}$Yb atoms are in excess with respect to the spin-polarized $^{171}$Yb particles have a very narrow stability range.