2017/09/28 by Gang Chen, Patrick A. Lee · 1 citation
Physics and Astronomy · #cond-mat.str-el #cond-mat.mtrl-sci
paper · pdf · doi:10.1103/physrevb.97.035124
published as Phys. Rev. B 97, 035124 (2018) · 12 pages, 13 figures
arxiv created 2017/09/28 · arxiv updated 2018/01/18
Motivated by the recent developments on cluster Mott insulating materials such as the cluster magnet LiZn2Mo3O8, we consider the strong plaquette charge ordered regime of the extended Hubbard model on a breathing Kagome lattice and reveal the properties of the cluster Mottness. The plaquette charge order arises from the inter-site charge interaction and the collective motion of three localized electrons on the hexagon plaquettes. This model leads naturally to a reduction of the local moments by 2/3 as observed in LiZn2Mo3O8. Furthermore, at low temperatures each hexagon plaquette contains an extra orbital-like degree of freedom in addition to the remaining spin 1/2. We explore the consequence of this emergent orbital degree of freedom. We point out the interaction between the local moments is naturally described by a Kugel-Khomskii spin-orbital model. We develop a parton approach and suggest a spin liquid ground state with spinon Fermi surfaces for this model. We further predict an emergent orbital order when the system is under a strong magnetic field. Various experimental consequences for LiZn2Mo3O8 are discussed, including an argument that the charge ordering much be short ranged if the charge per Mo is slightly off stoichiometry.