Triplet excitations in the frustrated spin ladder Li2Cu2O(SO4)2

Magnetic excitations of the recently discovered frustrated spin-1/2 two-leg ladder system Li2Cu2O(SO4)2 are investigated using inelastic neutron scattering, magnetic susceptibility, and infrared absorption measurements. Despite the presence of a magnetic dimerization concomitant with the tetragonal-...

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Bibliographic Details
Published in:Physical review. B 2019-02, Vol.99 (6), p.064416
Main Authors: Vaccarelli, O, Honecker, A, Giura, P, Béneut, K, Fåk, B, Rousse, G, Radtke, G
Format: Article
Language:English
Subjects:
Dimerization
Dimers
Excitation
Excitation spectra
First principles
Inelastic scattering
Infrared absorption
Magnetic permeability
Magnetism
Neutron scattering
Neutrons
Perturbation methods
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Summary:Magnetic excitations of the recently discovered frustrated spin-1/2 two-leg ladder system Li2Cu2O(SO4)2 are investigated using inelastic neutron scattering, magnetic susceptibility, and infrared absorption measurements. Despite the presence of a magnetic dimerization concomitant with the tetragonal-to-triclinic structural distortion occurring below 125 K, neutron scattering experiments reveal the presence of dispersive triplet excitations above a spin gap of Δ=10.6meV at 1.5K, a value consistent with the estimates extracted from magnetic susceptibility. The likely detection of these spin excitations in infrared spectroscopy is explained by invoking a dynamic Dzyaloshinskii-Moriya mechanism in which light is coupled to the dimer singlet-to-triplet transition through an optical phonon. These results are qualitatively explained by exact diagonalization and higher-order perturbation calculations carried out on the basis of the dimerized spin Hamiltonian derived from first principles.
ISSN:2469-9950
2469-9969
DOI:10.1103/PhysRevB.99.064416