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

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.