Extended supersolid phase of frustrated hard-core bosons on a triangular lattice

TL;DR

This paper investigates a frustrated hard-core boson model on a triangular lattice, demonstrating the existence of a supersolid phase in the large repulsion limit and mapping it to an unfrustrated case, revealing a broad supersolid region.

Contribution

The authors introduce a generalized Marshall sign rule and a dimer variational wavefunction to analyze the supersolid phase in frustrated boson systems on a triangular lattice.

Findings

Supersolid phase exists for large repulsion $V$ and hopping $t$ on the triangular lattice.

A unitary mapping relates frustrated and unfrustrated hopping cases, clarifying the phase structure.

The phase diagram for the triangular lattice spin 1/2 XXZ antiferromagnet is established.

Abstract

We study a model of hard-core bosons with frustrated nearest-neighbor hopping ($t$) and repulsion ($V$) on the triangular lattice. We argue for a supersolid ground state in the large repulsion ($V\gg|t|$) limit where a dimer representation applies, by constructing a unitary mapping to the well understood unfrustrated hopping case. This generalized 'Marshall sign rule' allows us to establish the precise nature of the supersolid order by utilizing a recently proposed dimer variational wavefunction, whose correlations can be efficiently calculated using the Grassman approach. By continuity, a supersolid is predicted over the wide parameter range, $V>-2t>0$. This also establishes a simple phase diagram for the triangular lattice spin 1/2 XXZ antiferromagnet.