Unveiling the Ground State Properties of the S =1/2 Kagome Heisenberg Antiferromagnet ZnCu3(OH)6Cl2 via Single Crystal NMR
e-mail: Satoru@issp.u-tokyo.ac.jp
The experimental quest for a quantum spin-liquid state (QSL) in frustrated magnetic systems serves fundamental scientific interests, as this intriguing quantum phase provides a fascinating platform for discovering exotic collective phenomena. The S=1/2 kagome Heisenberg antiferromagnet ZnCu3(OH)6Cl2 (herbertsmithite) is one of the leading contenders for an experimental realization of a QSL; in particular, the discovery of a continuum of spinon excitations using inelastic neutron scattering [1] has stimulated intense research into its physical properties. However, the nature of the paramagnetic ground state in this material remains highly debated, primarily owing to the difficulty in revealing the intrinsic magnetic behaviour of the kagome lattice from defect contributions. We will discuss our single crystal NMR measurements to probe the local spin susceptibility, low-frequency spin fluctuations, and the effects of defect Cu2+ spins occupying the Zn2+ sites. Most importantly, we demonstrate that the low- temperature behaviour of the intrinsic spin susceptibility provides direct evidence for a QSL state with a small energy gap in ZnCu3(OH)6Cl2 [2].
[1] T. H. Han, J. S. Helton, S. Chu, D. G. Nocera, J. A. Rodriguez-Rivera, C. Broholm and Y. S. Lee, Nature 492, 406 (2012).[2] M. Fu, T. Imai, T. H. Han and Y. S. Lee, Science 350, 655 (2015).
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