Supersolidity and phase diagram of softcore bosons in a triangular lattice

TL;DR

This paper investigates the phase diagram of softcore bosons on a triangular lattice, revealing multiple solid, superfluid, and supersolid phases, including newly predicted states, using quantum Monte Carlo simulations.

Contribution

It provides the first detailed phase diagram of softcore bosons on a triangular lattice, identifying new solid states and analyzing supersolid stability.

Findings

Four solid states identified at specific fillings

Supersolid phase exists between 1/3 and 2/3 fillings

New solid states (CDW II and CDW III) predicted

Abstract

We study the softcore extended Bose Hubbard model in a two-dimensional triangular lattice by using the quantum Monte Carlo methods. The ground state phase diagram of the system exhibits a very fruitful structure. Except the Mott insulating state, four kinds of solid states with respect to the commensurate filling factors $\rho=1/3,2/3$ and $\rho=1$ are identified. Two of them (CDW II and CDW III) are newly predicted. In incommensurate fillings, superfluid, spuersolid as well as phase separation states are detected . As in the case for the hardcore bosons, a supersolid phase exists in $1/3<\rho<2/3$ while it is unstable towards the phase separation in $\rho<1/3$. However, this instability is refrained in $2/3<\rho<1$ due to the softening of the bosons and then a supersolid phase survives.