Supersolidity from defect-condensation in the extended boson Hubbard model

TL;DR

This paper investigates the phase diagram of an extended boson Hubbard model, revealing the emergence of various supersolid states with distinct crystal structures and analyzing their superfluid properties and phase transitions.

Contribution

It provides a comprehensive analysis of supersolid phases in the extended boson Hubbard model using Gutzwiller mean field theory and quantum Monte Carlo simulations, highlighting new crystal structures and transition behaviors.

Findings

Identification of checkerboard, striped, and quarter-filled supersolid phases.

Observation of anisotropic superfluid density in striped supersolids.

First-order transition from striped to quarter-filled supersolid upon doping.

Abstract

We study the ground state phase diagram of the hard-core extended boson Hubbard model on the square lattice with both nearest- (nn) and next-nearest-neighbor (nnn) hopping and repulsion, using Gutzwiller mean field theory and quantum Monte Carlo simulations. We observe the formation of supersolid states with checkerboard, striped, and quarter-filled crystal structures, when the system is doped away from commensurate fillings. In the striped supersolid phase, a strong anisotropy in the superfluid density is obtained from the simulations; however, the transverse component remains finite, indicating a true two-dimensional superflow. We find that upon doping, the striped supersolid transitions directly into the supersolid with quarter-filled crystal structure, via a first-order stripe melting transition.