Route to supersolidity for the extended Bose-Hubbard model

TL;DR

This paper investigates the phase diagram of the extended Bose-Hubbard model, revealing conditions under which a large supersolid phase exists, especially relevant for experiments with dipolar Bose gases in optical lattices.

Contribution

It demonstrates that for 2dV > U, the supersolid phase occupies a much larger region, with a phase boundary increasing linearly with hopping, enhancing experimental observability.

Findings

Supersolid phase is larger when 2dV > U.

Superfluid boundary increases linearly with hopping for 2dV U.

Potential for observing supersolidity in dipolar Bose gases is significantly improved.

Abstract

We use the Gutzwiller ansatz and analyze the phase diagram of the extended Bose-Hubbard Hamiltonian with on-site (U) and nearest-neighbor (V) repulsions. For $d$-dimensional hypercubic lattices, when 2dV < U, it is well-known that the ground state alternates between the charge-density-wave (CDW) and Mott insulators, and the supersolid (SS) phase occupies small regions around the CDW insulators. However, when 2dV > U, in this paper, we show that the ground state has only CDW insulators, and more importantly, the SS phase occupies a much larger region in the phase diagram, existing up to very large hopping values which could be orders of magnitude higher than that of the well-known case. In particular, the SS-superfluid phase boundary increases linearly as a function of hopping when 2dV \gtrsim 1.5U, for which the prospects of observing the SS phase with dipolar Bose gases loaded into optical lattices is much higher.