Supersolid and charge density-wave states from anisotropic interaction in an optical lattice

TL;DR

This paper demonstrates how anisotropic dipole interactions in an optical lattice can stabilize novel quantum phases, including supersolids and charge density waves, using advanced numerical simulations.

Contribution

It introduces a new anisotropic Hubbard model for hard-core bosons and maps out its phase diagram, revealing phases not previously characterized in this context.

Findings

Identification of striped and checkerboard charge density wave states

Discovery of a supersolid phase connecting superfluid and solid states

Different transition mechanism to supersolidity compared to soft-core models

Abstract

We show anisotropy of the dipole interaction between magnetic atoms or polar molecules can stabilize new quantum phases in an optical lattice. Using a well controlled numerical method based on the tensor network algorithm, we calculate phase diagram of the resultant effective Hamiltonian in a two-dimensional square lattice - an anisotropic Hubbard model of hard-core bosons with attractive interaction in one direction and repulsive interaction in the other direction. Besides the conventional superfluid and the Mott insulator states, we find the striped and the checkerboard charge density wave states and the supersolid phase that interconnect the superfluid and the striped solid states. The transition to the supersolid phase has a mechanism different from the case of the soft-core Bose Hubbard model.