Quantum and classical dynamics in complex one-dimensional antiferromagnets


Abstract in English

Of great recent interest in condensed matter physics are phenomena of coexistence of quantum and classical properties in the same material. Such duality occurs in certain mixed-spin antiferromagnets composed of quantum spin chains interacting through ``auxiliary magnetic ions. In this category are linear-chain rare earth nickelates that exhibit a seemingly paradoxical co-existence of long-range magnetic order and one-dimensional gapped quantum spin excitations at low temperatures. In the present paper we propose a unified physical description of these compounds, supported by recent neutron diffraction and inelastic scattering studies. Our basic concept is the effective separation between low-frequency classical and high-frequency quantum spin correlations. This interpretation enables experimental measurements of some previously inaccessible fundamental properties of quantum spin chains, and predicts new exotic magnetic excitations and mechanisms of long-range ordering in complex quantum magnets.

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