title: Resonating-valence-bond States and ferromagnetic correlations in the doped triangular Mott insulator.
abstract: The two-dimensional t-J model on a triangular lattice is studied using high-temperature expansions. By studying the entropy and spin susceptibility, we find that the sign of the hopping integral t is very crucial. In the case of t>0, the peak of the spin susceptibility moves to the high-temperature region with hole doping, which indicates the appearance of the resonating-valence-bond state. In contrast, for t<0, the peak of the spin susceptibility disappears with hole doping and the entropy at low temperatures behaves as S=gammaT with large coefficient gamma, representing a large effective mass. This behavior is understood from the competition between Nagaoka's ferromagnetism and singlet formation.
authors.affiliation: Department of Physics, University of Tokyo, Bunkyo-ku Tokyo 113-0033, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Koretsune
authors.forename: Masao
authors.initials: M
authors.lastname: Ogata