60 research outputs found
Ground State of a Spin System with Two- and Four-spin Exchange Interactions on the Triangular Lattice
We study a spin system with both two- and four-spin exchange interactions on
the triangular lattice as a possible model for the nuclear magnetism of solid
He layers adsorbed on grafoil. The ground state is analyzed by the use of
the mean-field approximation. It is shown that the four-sublattice state is
favored by introduction of the four-spin exchange interaction. A possible phase
transition at a finite temperature into a phase with the scalar chirality is
predicted. Application of a magnetic field is shown to cause a variety of phase
transitions.Comment: 5 pages, Revte
Nematic order in square lattice frustrated ferromagnets
We present a new scenario for the breakdown of ferromagnetic order in a
two-dimensional quantum magnet with competing ferromagnetic and
antiferromagnetic interactions. In this, dynamical effects lead to the
formation of two-magnon bound states, which undergo Bose-Einstein condensation,
giving rise to bond-centered nematic order. This scenario is explored in some
detail for an extended Heisenberg model on a square lattice. In particular, we
present numerical evidence confirming the existence of a state with d-wave
nematic correlations but no long range magnetic order, lying between the
saturated ferromagnetic and collinear antiferromagnetic phases of the
ferromagnetic J1-J2 model. We argue by continuity of spectra that this phase is
also present in a model with 4-spin cyclic exchange.Comment: 5 pages latex + 5 eps figures, accpeted for publication in Phys. Rev.
Let
NMR relaxation rate and dynamical structure factors in nematic and multipolar liquids of frustrated spin chains under magnetic fields
Recently, it has been shown that spin nematic (quadrupolar) or higher
multipolar correlation functions exhibit a quasi long-range order in the wide
region of the field-induced Tomonaga-Luttinger-liquid (TLL) phase in spin-1/2
zigzag chains. In this paper, we point out that the temperature dependence of
the NMR relaxation rate 1/T_1 in these multipolar TLLs is qualitatively
different from that in more conventional TLLs of one-dimensional quantum
magnets (e.g., the spin-1/2 Heisenberg chain); 1/T_1 decreases with lowering
temperature in multipolar TLL. We also discuss low-energy features in spin
dynamical structure factors which are characteristic of the multipolar TLL
phases.Comment: 4+epsilon pages, 2 figures, published versio
Finite temperature Mott transition in Hubbard model on anisotropic triangular lattice
We investigate the Hubbard model on the anisotropic triangular lattice by
means of the cellular dynamical mean field theory. The phase diagram determined
in the Hubbard interaction versus temperature plane shows novel reentrant
behavior in the Mott transition due to the competition between Fermi-liquid
formation and magnetic correlations under geometrical frustration. We
demonstrate that the reentrant behavior is characteristic of the Mott
transition with intermediate geometrical frustration and indeed consistent with
recent experimental results of organic materials.Comment: 5 pages, 6 figure
- …