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arXiv · 1811.04674

Spin Triplet Ground-State in the Copper Hexamer Compounds A2Cu3O(SO4)3 (A=Na,K)

A. Furrer·A. Podlesnyak·E. Pomjakushina·V. Pomjakushin
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Abstract

The compounds A2Cu3O(SO4)3 (A=Na,K) are characterized by copper hexamers which are weakly coupled along the b-axis to realize one-dimensional antiferromagnetic chains below TN=3 K, whereas the interchain interactions along the a- and c-axes are negligible. We investigated the energy-level splittings of the copper hexamers by inelastic neutron scattering below and above TN. The eight lowest-lying hexamer states could be unambiguously assigned and parametrized in terms of a Heisenberg exchange Hamiltonian, providing direct experimental evidence for an S=1 triplet ground-state associated with the copper hexamers. Therefore, the compounds A2Cu3O(SO4)3 serve as novel cluster-based spin-1 antiferromagnets to support Haldane's conjecture that a gap appears in the excitation spectrum below TN, which was verified by inelastic neutron scattering.

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A. Furrer, A. Podlesnyak, E. Pomjakushina, V. Pomjakushin. 2018-11-12. Spin Triplet Ground-State in the Copper Hexamer Compounds A2Cu3O(SO4)3 (A=Na,K). https://doi.org/10.1103/physrevb.98.180410

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