Staggered superfluid phases of dipolar bosons in two-dimensional square lattices

TL;DR

This paper investigates the ground states of dipolar bosons in a 2D lattice, revealing staggered superfluid and supersolid phases driven by dipolar interactions and correlated hopping effects.

Contribution

It introduces a detailed phase diagram for dipolar bosons in 2D lattices, highlighting the emergence of staggered superfluid and supersolid phases due to correlated hopping.

Findings

Staggered superfluid and supersolid phases occur at zero kinetic energy.

Interference between correlated hopping and tunneling influences phase stability.

Comparison with other methods validates the phase diagram.

Abstract

We study the quantum ground state of ultracold bosons in a two-dimensional square lattice. The bosons interact via the repulsive dipolar interactions and s-wave scattering. The dynamics is described by the extended Bose-Hubbard model including correlated hopping due to the dipolar interactions, the coefficients are found from the second quantized Hamiltonian using the Wannier expansion with realistic parameters. We determine the phase diagram using the Gutzwiller ansatz in the regime where the coefficients of the correlated hopping terms are negative and can interfere with the tunneling due to single-particle effects. We show that this interference gives rise to staggered superfluid and supersolid phases at vanishing kinetic energy, while we identify parameter regions at finite kinetic energy where the phases are incompressible. We compare the results with the phase diagram obtained with the cluster Gutzwiller approach and with the results found in one dimension using DMRG.