Absence of Bose condensation on lattices with moat bands

TL;DR

This paper investigates hard-core bosons on frustrated lattices with moat bands, revealing that at low densities the ground state is noncondensed and exhibits incompressible liquid domains, challenging expectations of Bose condensation.

Contribution

It demonstrates the absence of Bose condensation on lattices with moat bands and introduces a fermionic description with Chern-Simons gauge fields for the ground state.

Findings

Ground state is noncondensed at low density.

Presence of incompressible liquid domains at fixed densities.

No Bose condensation occurs on moat band lattices.

Abstract

We study hard-core bosons on a class of frustrated lattices with the lowest Bloch band having a degenerate minimum along a closed contour, the moat, in the reciprocal space. We show that at small density the ground state of the system is given by a noncondensed state, which may be viewed as a state of fermions subject to Chern-Simons gauge field. At fixed density of bosons, such a state exhibits domains of incompressible liquids. Their fixed densities are given by fractions of the reciprocal-space area enclosed by the moat.