Ground-State Phase Diagram of the Two-Dimensional Extended Bose-Hubbard Model

TL;DR

This study maps the ground-state phase diagram of the two-dimensional extended Bose-Hubbard model, revealing a broad supersolid phase region at various fillings and large hopping, using unbiased quantum Monte Carlo simulations.

Contribution

It provides the first comprehensive phase diagram including large hopping parameters, showing supersolid phases below, at, and above half-filling, extending previous studies.

Findings

Supersolid phase exists below and at half-filling for large hopping.

Broad supersolid region observed under strong nearest-neighbor repulsion.

Results qualitatively agree with Gutzwiller mean-field predictions.

Abstract

We investigate the ground-state phase diagram of the soft-core Bose-Hubbard model with the nearest-neighbor repulsion on a square lattice by using an unbiased quantum Monte Carlo method. In contrast to the previous study[P. Sengupta {\it et. al.}, Phys. Rev. Lett. {\bf 94}, 207202 (2005)], we present the ground-state phase diagrams up to large hopping parameters. As a result, in addition to the known supersolid above half-filling, we find supersolid even below and at half-filling for large hopping parameters. Furthermore, for the strong nearest-neighbor repulsion, we show that the supersolid phase occupies a remarkably broad region in the phase diagram. The results are in qualitative agreement with that obtained by the Gutzwiller mean-field approximation[M. Iskin, Phys. Rev. A {\bf 83}, 051606(R) (2011) and T. Kimura, Phys. Rev. A {\bf 84}, 063630 (2011)].