Unveiling the Ground State Properties of S=1/2 Kagomé-lattice Heisenberg Antiferromagnet ZnCu₃(OH)₆Cl₂ using Single Crystal NMR

Mingxuan Fu (McMaster University)

The S=1/2 kagomé-lattice Heisenberg antiferromagnet ZnCu₃(OH)₆Cl₂ (herbertsmithite) is the leading contender for an experimental realization of a quantum spin-liquid state. The recent inelastic neutron scattering measurements on single crystals of ZnCu₃(OH)₆Cl₂ [1] revealed a spinon continuum in its spin excitation spectrum, in contrast to the conventional magnons expected in magnetically ordered states. This discovery has drawn strong attention to its exotic magnetic properties.

Nonetheless, the nature of the paramagnetic ground state in ZnCu₃(OH)₆Cl₂ remains hotly debated. The root cause of the controversy lies in the difficulty in untangling the effects of defects from the intrinsic properties of the kagome lattice. We conducted ¹⁷O and ²D NMR experiments on ZnCu₃(OH)₆Cl₂ single crystals [2,3], and succeeded in distinguishing the intrinsic properties of the kagomé-lattice from the defect-induced phenomena. In particular, our ¹⁷O NMR results provide direct experimental evidence for a gapped quantum spin-liquid state realized in ZnCu₃(OH)₆Cl₂.

[1] T. Han. et al., Nature 492 (2012) 406.
[2] M. Fu, T. Imai. et al., manuscript submitted for publication.
[3] T. Imai, M. Fu. et al., PRB 84 (2012) 020411R. Also see T. Imai. et al., PRL 100 (2008) 077203.

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