Coulomb liquid phases of bosonic cluster Mott insulators on a pyrochlore lattice

TL;DR

This study uses quantum Monte Carlo simulations to map out the phase diagram of bosonic particles on a pyrochlore lattice, revealing Coulomb liquid phases in cluster Mott insulators with specific fillings, described by emergent U(1) gauge theory.

Contribution

It identifies and characterizes three distinct cluster Mott insulator phases as Coulomb liquids with emergent U(1) gauge fields on the pyrochlore lattice.

Findings

Three cluster Mott insulator phases at 1/4, 1/2, and 3/4 fillings.

All phases exhibit Coulomb liquid behavior consistent with U(1) quantum electrodynamics.

Correlation functions match theoretical predictions for emergent gauge fields.

Abstract

Employing large-scale quantum Monte Carlo simulations, we reveal the full phase diagram of the extended Hubbard model of hard-core bosons on the pyrochlore lattice with partial fillings. When the intersite repulsion is dominant, the system is in a cluster Mott insulator phase with an integer number of bosons localized inside the tetrahedral units of the pyrochlore lattice. We show that the full phase diagram contains three cluster Mott insulator phases with 1/4, 1/2, and 3/4 boson fillings, respectively. We further demonstrate that all three cluster Mott insulators are Coulomb liquid phases and its low-energy property is described by the emergent compact U(1) quantum electrodynamics. In addition to measuring the specific heat and entropy of the cluster Mott insulators, we investigate the correlation function of the emergent electric field and verify it is consistent with the compact U(1) quantum electrodynamics description. Our result sheds light on the magnetic properties of various pyrochlore systems, as well as the charge physics of the cluster magnets.