The disordered ground-state properties of a double-layer quantum antiferromagnet are investigated in the bond operator representation. The intralayer and interlayer couplings are J and J perpendicular to , respectively. In a mean-field approximation, we obtain a spin gap which decreases with increasing ratio lambda =J/J perpendicular to and disappears at the value lambda c =0.292. In the region 0<or= lambda <or= lambda c , we calculate the disordered ground-state energy, the intralayer and interlayer nearest-neighbour singlet strengths, and the correlation length.The disordered ground-state properties of a double-layer quantum antiferromagnet are investigated in the bond operator representation. The intralayer and interlayer couplings are J and J perpendicular to , respectively. In a mean-field approximation, we obtain a spin gap which decreases with increasing ratio lambda =J/J perpendicular to and disappears at the value lambda c =0.292. In the region 0<or= lambda <or= lambda c , we calculate the disordered ground-state energy, the intralayer and interlayer nearest-neighbour singlet strengths, and the correlation length.

Journal of Physics Condensed MatterNov 13, 19956 citations

The anisotropic quantum antiferromagnet on the Sierpinski gasket : ground state and thermodynamics

Voigt, A., Wolfgang Wenzel, Johannes Richter +1 more

We investigate an antiferromagnetic s=1/2 quantum spin system with anisotropic spin exchange on a fractal lattice, the Sierpinski gasket. We introduce a novel approximative numerical method, the configuration selective diagonalization (CSD) and apply this method to a the Sierpinski gasket with N=42. Using this and other methods we calculate ground state energies, spin gap, spin-spin correlations and specific heat data and conclude that the s=1/2 quantum antiferromagnet on the Sierpinski gasket shows a disordered magnetic ground state with on the Sierpinski gasket shows a disordered magnetic ground state with a very short correlation length of xiapproximate to1 and an, albeit very small, spin gap. This conclusion holds for Heisenberg as well a for XY exchange.We investigate an antiferromagnetic s=1/2 quantum spin system with anisotropic spin exchange on a fractal lattice, the Sierpinski gasket. We introduce a novel approximative numerical method, the configuration selective diagonalization (CSD) and apply this method to a the Sierpinski gasket with N=42. Using this and other methods we calculate ground state energies, spin gap, spin-spin correlations and specific heat data and conclude that the s=1/2 quantum antiferromagnet on the Sierpinski gasket shows a disordered magnetic ground state with on the Sierpinski gasket shows a disordered magnetic ground state with a very short correlation length of xiapproximate to1 and an, albeit very small, spin gap. This conclusion holds for Heisenberg as well a for XY exchange.

Jan 1, 20042 citations

Quantum disordered ground states in frustrated antiferromagnets with multiple ring exchange interactions

Satoshi Fujimoto

We present a certain class of two-dimensional frustrated quantum Heisenberg spin systems with multiple ring exchange interactions which are rigorously demonstrated to have quantum disordered ground states without magnetic long-range order. The systems considered in this paper are $s=1∕2$ antiferromagnets on a honeycomb and square lattices, and an $s=1$ antiferromagnet on a triangular lattice. We find that for a particular set of parameter values, the ground state is a short-range resonating valence bond state or a valence bond crystal state. It is shown that these systems are closely related to the quantum dimer model introduced by Rokhsar and Kivelson as an effective low-energy theory for valence bond states.We present a certain class of two-dimensional frustrated quantum Heisenberg spin systems with multiple ring exchange interactions which are rigorously demonstrated to have quantum disordered ground states without magnetic long-range order. The systems considered in this paper are $s=1∕2$ antiferromagnets on a honeycomb and square lattices, and an $s=1$ antiferromagnet on a triangular lattice. We find that for a particular set of parameter values, the ground state is a short-range resonating valence bond state or a valence bond crystal state. It is shown that these systems are closely related to the quantum dimer model introduced by Rokhsar and Kivelson as an effective low-energy theory for valence bond states.

arXiv:cond-mat/0501698Physical Review BJul 14, 200527 citations

s=1∕2

antiferromagnets on a honeycomb and square lattices, and an

s=1

antiferromagnet on a triangular lattice. We find that for a particular set of parameter values, the ground state is a short-range resonating valence bond state or a valence bond crystal state. It is shown that these systems are closely related to the quantum dimer model introduced by Rokhsar and Kivelson as an effective low-energy theory for valence bond states.