Antiferromagnetic behavior in self-bound one-dimensional composite bosons

Abstract

The structure of self-bound one-dimensional droplets containing a mixture of Ytterbium fermionic isotopes ($^{173}$Yb, $^{171}$Yb) is calculated by means of a diffusion Monte Carlo technique. We considered only balanced setups in which all the atoms of one isotope are spin-polarized, while the atoms of the other can have up to three different spin values, that difference being a necessary requirement to achieve stable systems. Our results indicate that these droplets consist of consecutive "molecules" made up of one $^{173}$Yb and one $^{171}$Yb atom. In other words, we have up to three different kinds of composite bosons, corresponding to the number of spin components in the non-polarized isotope. The fermionic nature of those Yb atoms makes pairs with identical spin composition avoid each other, creating a Pauli-like-hole filed by another molecule in which at least one of the Yb atoms has a different spin from that of their closest neighbors. This effective repulsion is akin to an antiferromagnetic short-range interaction between different kinds of composite bosons.