title: Effective spin model for the spin-liquid phase of the Hubbard model on the triangular lattice.
abstract: We show that the spin-liquid phase of the half-filled Hubbard model on the triangular lattice can be described by a pure spin model. This is based on a high-order strong coupling expansion (up to order 12) using perturbative continuous unitary transformations. The resulting spin model is consistent with a transition from three-sublattice long-range magnetic order to an insulating spin-liquid phase, and with a jump of the double occupancy at the transition. Exact diagonalizations of both models show that the effective spin model is quantitatively accurate well into the spin-liquid phase, and a comparison with the Gutzwiller projected Fermi sea suggests a gapless spectrum and a spinon Fermi surface.
authors.affiliation: Lehrstuhl für Theoretische Physik I, TU Dortmund, Dortmund, Germany.
authors.forename: Hong-Yu
authors.initials: HY
authors.lastname: Yang
authors.forename: Andreas M
authors.initials: AM
authors.lastname: Läuchli
authors.forename: Frédéric
authors.initials: F
authors.lastname: Mila
authors.forename: Kai Phillip
authors.initials: KP
authors.lastname: Schmidt