Solid phases and pairing in a mixture of polar molecules and atoms

TL;DR

This study explores how adding atoms to a polar molecule mixture on a lattice enhances the stability of solid and supersolid phases, enabling their existence at lower dipolar interactions and higher temperatures.

Contribution

It demonstrates that atom-molecule interactions can stabilize solid and supersolid phases at lower interaction strengths and higher temperatures, revealing new phases in the two-component Bose-Hubbard model.

Findings

Solid phases are stabilized at lower dipolar interactions due to atom presence.

Atoms form solid phases with melting temperatures matching molecules.

Large atom-molecule interactions can lead to a paired supersolid phase.

Abstract

We consider a mixture of hard core bosonic polar molecules, interacting via repulsive dipole-dipole interaction, and one atomic bosonic species. The mixture is confined on a two-dimensional square lattice and, at low enough temperatures, can be described by the two-component Bose-Hubbard model. The latter displays a extremely rich phase diagram including solid, superfluid, supersolid phases. Here we mainly focus on the checkerboard molecular solid, stabilized by the long range dipolar interaction, and study how the presence of atoms affects its robustness both at zero and finite temperature. We find that, due to atom-molecule interaction, solid phases can be stabilized at both, (much) lower strengths of dipolar interaction and higher temperatures, than when no atoms are present. As a byproduct, atoms also order in a solid phase with same melting temperatures as for molecules. Finally, we find that for large enough interaction between atoms and molecules a paired supersolid phase can be stabilized.