title: Absence of superconductivity and valence bond order in the Hubbard-Heisenberg model for organic charge-transfer solids.
abstract: A frustrated, effective ½-filled band Hubbard-Heisenberg model has been proposed for describing the strongly dimerized charge-transfer solid families κ-(ET)2X and Z[Pd(dmit)2]2. In addition to showing unconventional superconductivity, these materials also exhibit antiferromagnetism, candidate spin-liquid phases, and, in the case of Z=EtMe3P, a spin-gapped phase that has sometimes been referred to as a valence bond solid. We show that neither superconductivity nor the valence bond order phase occurs within the Hubbard-Heisenberg model. We suggest that a description based on ¼-filling, that is reached when the carrier concentration per molecule instead of per dimer is considered, thus may be appropriate.
authors.affiliation: Department of Physics, University of Arizona, Tucson, AZ 85721, USA.
authors.forename: N
authors.initials: N
authors.lastname: Gomes
authors.forename: R T
authors.initials: RT
authors.lastname: Clay
authors.forename: S
authors.initials: S
authors.lastname: Mazumdar