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      Generalized Hardcore Dimer Models approach to low-energy Heisenberg frustrated antiferromagnets: general properties and application to the kagome antiferromagnet

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          Abstract

          We propose a general non-perturbative scheme that quantitatively maps the low-energy sector of spin-1/2 frustrated Heisenberg antiferromagnets to effective Generalized Quantum Dimer Models. We develop the formal lattice independent frame and establish some important results on (i) the locality of the generated Hamiltonians (ii) how full resummations can be performed in this renormalization scheme. The method is then applied to the much debated kagome antiferromagnet for which a fully resummed effective Hamiltonian - shown to capture the essential properties and provide deep insights on the microscopic model [D. Poilblanc, M. Mambrini and D. Schwandt, arXiv:0912.0724] - is derived.

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          Numerical studies of a 36-sitekagome´ antiferromagnet

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            Order versus Disorder in the Quantum Heisenberg Antiferromagnet on the Kagom{\'e} lattice: an approach through exact spectra analysis

            A group symmetry analysis of the low lying levels of the spin-1/2 kagom\'e Heisenberg antiferromagnet is performed for small samples up to N=27. This approach allows to follow the effect of quantum fluctuations when the sample size increases. The results contradict the scenario of ``order by disorder'' which has been advanced on the basis of large S calculations. A large enough second neighbor ferromagnetic exchange coupling is needed to stabilize the \(\sqrt 3 \times \sqrt 3\) pattern: the finite size analysis indicates a quantum critical transition at a non zero coupling.
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              Low-energy sector of the S=1/2 Kagome antiferromagnet

              Starting from a modified version of the the S=1/2 Kagome antiferromagnet to emphasize the role of elementary triangles, an effective Hamiltonian involving spin and chirality variables is derived. A mean-field decoupling that retains the quantum nature of these variables is shown to yield a Hamiltonian that can be solved exactly, leading to the following predictions: i) The number of low lying singlet states increase with the number of sites N like 1.15 to the power N; ii) A singlet-triplet gap remains in the thermodynamic limit; iii) Spinons form boundstates with a small binding energy. By comparing these properties with those of the regular Kagome lattice as revealed by numerical experiments, we argue that this description captures the essential low energy physics of that model.
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                Author and article information

                Journal
                03 February 2010
                2010-04-11
                Article
                10.1103/PhysRevB.81.214413
                1002.0774
                b7d3d7ef-36c0-4d9a-920d-88a64b6003c1

                http://arxiv.org/licenses/nonexclusive-distrib/1.0/

                History
                Custom metadata
                Phys. Rev. B 81, 214413 (2010)
                26 pages, 4 figures, EPAPS inlined, manuscript revised, corrected minor typos (notably figure 2).
                cond-mat.str-el

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