Density wave patterns for fermionic dipolar molecules on a square optical lattice: Mean-field-theory analysis

TL;DR

This paper investigates the phase diagram of ultracold fermionic dipolar molecules on a 2D square lattice, revealing various density wave phases and phase separation using mean-field theory and Monte Carlo analysis.

Contribution

It provides a mean-field phase diagram for dipolar molecules on a lattice, highlighting the stability of density wave phases and the suppression of higher-period phases.

Findings

Multiple density wave phases identified

Phase separation observed between phases

Higher-period phases suppressed in exact solutions

Abstract

We model a system of ultracold fermionic dipolar molecules on a two-dimensional square lattice. Assuming that the molecules are in their nondegenerate hyperfine ground state, and that the dipole moment is polarized perpendicular to the plane (as in the recent experiments on 40K-87Rb molecules), we approximate these molecules as spinless fermions with long range repulsive dipolar interactions. We use mean field theory to obtain the restricted phase diagram as a function of the filling, the strength of interaction and the temperature. We find a number of ordered density wave phases in the system, as well as phase separation between these phases. A Monte Carlo analysis shows that the higher-period phases are usually suppressed in the exact solution.