Quantum Melting of Valence Bond Crystal Insulators and Novel Supersolid Phase at Commensurate Density

TL;DR

This study investigates the quantum melting of valence bond crystal insulators into superfluid phases and uncovers a novel supersolid phase at specific densities using numerical simulations of Hubbard models.

Contribution

It introduces the discovery of a new commensurate VBC supersolid phase and compares behaviors of bosons and fermions under various conditions.

Findings

Valence bond crystals are stabilized at certain densities.

Melting of VBCs leads to superfluid/metallic phases.

A novel supersolid phase is identified as a precursor to melting.

Abstract

Bosonic and fermionic Hubbard models on the checkerboard lattice are studied numerically for infinite on-site repulsion. At particle density n=1/4 and strong nearest-neighbor repulsion, insulating Valence Bond Crystals (VBC) of resonating particle pairs are stabilized. Their melting into superfluid/metallic phases under increasing hopping is investigated at T=0K. More specifically, we identify a novel and unconventional commensurate VBC supersolid region, precursor to the melting of the bosonic crystal. Hardcore bosons (spins) are compared to fermions (electrons), as well as positive to negative (frustrating) hoppings.