title: Bold diagrammatic Monte Carlo method applied to fermionized frustrated spins.
abstract: We demonstrate, by considering the triangular lattice spin-1/2 Heisenberg model, that Monte Carlo sampling of skeleton Feynman diagrams within the fermionization framework offers a universal first-principles tool for strongly correlated lattice quantum systems. We observe the fermionic sign blessing--cancellation of higher order diagrams leading to a finite convergence radius of the series. We calculate the magnetic susceptibility of the triangular-lattice quantum antiferromagnet in the correlated paramagnet regime and reveal a surprisingly accurate microscopic correspondence with its classical counterpart at all accessible temperatures. The extrapolation of the observed relation to zero temperature suggests the absence of the magnetic order in the ground state. We critically examine the implications of this unusual scenario.
authors.affiliation: Department of Physics, University of Massachusetts, Amherst, Massachusetts 01003, USA and Institute for Nuclear Research of Russian Academy of Sciences, 117312 Moscow, Russia.
authors.forename: S A
authors.initials: SA
authors.lastname: Kulagin
authors.affiliation: Department of Physics, University of Massachusetts, Amherst, Massachusetts 01003, USA and Russian Research Center "Kurchatov Institute," 123182 Moscow, Russia.
authors.forename: N
authors.initials: N
authors.lastname: Prokof'ev
authors.affiliation: Department of Physics and Astronomy, University of Utah, Salt Lake City, Utah 84112, USA.
authors.forename: O A
authors.initials: OA
authors.lastname: Starykh
authors.affiliation: Department of Physics, University of Massachusetts, Amherst, Massachusetts 01003, USA and Russian Research Center "Kurchatov Institute," 123182 Moscow, Russia.
authors.forename: B
authors.initials: B
authors.lastname: Svistunov
authors.affiliation: Department of Physics, University of Massachusetts, Amherst, Massachusetts 01003, USA.
authors.forename: C N
authors.initials: CN
authors.lastname: Varney