Study of a hard-core boson model with ring-only interactions

TL;DR

This study uses Quantum Monte Carlo simulations to explore a hardcore boson model with ring-only interactions on a square lattice, revealing various phases including charge density wave, valence bond solid, and a potentially stable Exciton Bose Liquid phase.

Contribution

It provides the first detailed phase diagram of a ring-only hardcore boson model, identifying conditions for the emergence of the Exciton Bose Liquid phase.

Findings

Charge density wave phase at small K2

Valence bond solid phase at intermediate K2

Possible stable Exciton Bose Liquid phase at larger K2

Abstract

We present a Quantum Monte Carlo study of a hardcore boson model with ring-only exchanges on a square lattice, where a $K_1$ term acts on 1$\times$1 plaquettes and a $K_2$ term acts on 1$\times$2 and 2$\times$1 plaquettes. At half-filling, the phase diagram reveals charge density wave for small $K_2$, valence bond solid for intermediate $K_2$, and possibly for large $K_2$ the novel Exciton Bose Liquid (EBL) phase first proposed by Paramekanti, et al[Phys. Rev. B {\bf 66}, 054526 (2002)]. Away from half-filling, the EBL phase is present already for intermediate $K_2$ and remains stable for a range of densities below 1/2 before phase separation sets in at lower densities