Numerical Study of Magnetic Raman Scattering Spectra in Ladder Antiferromagnets —Exchange Scatterings from the Singlet Ground State—

概要

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The exchange-scattering spectra are reproduced by the numerical calculation for the finite Heisenberg ladder, in which two-legs with antiferromagnetic bond Jc is connected by rungs with antiferromagnetic bond Jr. The numerical calculation is made for the system of 12 ×2 sites by Lanczos method. The ratio of Jc/Jr is considered to be 0.6–1.0 in order to discuss the experimental work for ladders of Cu2+ ions in oxide compounds Sr14-xCaxCu24O41. In addition to the Raman edge about Jr corresponding twice the singlet-triplet spin gap, the characteristic structure appears around 2 or 3 times of Jr i.e. 3 or 5 times the spin-gap. We concentrate our attention on characteristic features of excited levels, transitions to which are Raman-active. In particular, the relationship between correlations for spins in those states and corresponding Raman intensities is discussed in the picture of triplet pairs excited from singlet dimers. By the perturbation theory, the essential dependence of those intensities on distances between triplet dimers is investigated.
Physical Society of Japanの論文
2001-08-15