Schedule Oct 12, 2012
A Phenomenological Theory for the Z2 Spin Liquid Phase of Kagome Heisenberg Antiferromagnet
Yuan Wan (JHU)

Authors: Yuan Wan and Oleg Tchernyshyov

Department of Physics and Astronomy, the Johns Hopkins University, Baltimore, Maryland, 21218

Quantum spin liquids are novel quantum phases supporting fractionalized quasi-particles. Highly frustrated magnets provide a natural ground for the search of quantum spin liquids [1]. The spin-1/2 kagome Heisenberg antiferromagnet (KHAF) stands out as one of the most promising candidate systems [2]. However, the precise nature of its ground state is still under active debate. Recent numerical calculations based on density-matrix renormalization group (DMRG) show evidence for a possible Z2 spin liquid phase, the effective description of which is a Z2 gauge theory [3,4]. Yet, the DMRG calculations alone cannot tell the explicit form of the effective theory.

In this work, we construct a minimal Z2 gauge Hamiltonian encapsulating the DMRG phenomenology in the S=0 sector. We generalize Misguich's Hamiltonian [5] by including dimer density interactions [6]. We show that our minimal model naturally produces the diamond resonance pattern observed in DMRG. Moreover, we show that the puzzling boundary effects are easily explained by our model.  We also calculate the valence-bond pattern induced by a pinned singlet and by an open boundary, both agreeing well with the DMRG calculations.

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[3]S. Yan, D. A. Huse, and S. R. White, Science 332, 1173 (2011).
[4]S. Depenbrock, I. P. McCulloch, and U. Schollwöck, Phys. Rev. Lett. 109, 067201 (2012).
[5]G. Misguich, D. Serban, and V. Pasquier, Phys. Rev. Lett. 89, 137202 (2002).
[6]Y. Huh, M. Punk, and S. Sachdev, Phys. Rev. B 84, 094419 (2011).

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