Plaquette bond order wave in the quarter-filled extended Hubbard model on the checkerboard lattice

TL;DR

This study investigates an extended Hubbard model on a frustrated checkerboard lattice, revealing a valence bond plaquette phase at quarter-filling through multiple computational methods, with a degenerate ground state that breaks translation symmetry.

Contribution

It provides the first comprehensive evidence for a plaquette bond order wave in the quarter-filled extended Hubbard model on the checkerboard lattice using combined theoretical approaches.

Findings

Identification of a valence bond plaquette phase at quarter-filling.

Ground state exhibits twofold degeneracy and broken translation symmetry.

Bond energies show staggering while charge distribution remains uniform.

Abstract

An extended Hubbard model (including nearest-neighbor repulsion and antiferromagnetic spin exchange) is investigated on the frustrated checkerboard lattice, a two-dimensional analog of the pyrochlore lattice. Combining Gutzwiller renormalized mean-field (MF) calculations, exact diagonalization (ED) techniques, and a weak-coupling renormalization group (RG) analysis we provide strong evidence for a crystalline valence bond plaquette phase at quarter-filling. The ground state is twofold degenerate and breaks translation symmetry. The bond energies show a staggering while the charge distribution remains uniform.