Two-magnon Raman scattering in spin-ladder geometries and the ratio of rung and leg exchange constants

Abstract

We discuss ways in which the ratio of exchange constants along the rungs and legs of a spin-ladder material influences the two-magnon Raman scattering spectra and hence can be determined from it. We show that within the Fleury-Loudon-Elliott approach, the Raman line-shape does not change with polarization geometries. This lineshape is well known to be difficult to calculate accurately from theory. However, the Raman scattering intensities do vary with polarization geometries, which are easy to calculate. With some assumptions about the Raman scattering Hamiltonian, the latter can be used to estimate the ratio of exchange constants. We apply these results to Sugai's recent measurements of Raman scattering from spin-ladder materials such as La${}_6$Ca${}_8$Cu${}_{24}$O${}_{41}$ and Sr${}_{14}$Cu${}_{24}$O${}_{41}$.

5 pages, revtex. Latest version focuses on ladder materials, with a detailed examination of the role of Heisenberg-like coupling constants which appear in the Fleury-Loudon-Elliott scattering operator but are rarely discussed in the literature

References in corpus (3)

• Experiments on Ladders Reveal a Complex Interplay between a Spin-Gapped Normal State and Superconductivity
• Optical Properties of the Spin-Ladder Compound Sr_{14}Cu_{24}O_{41}
• Two-magnon Raman scattering in insulating cuprates: Modifications of the effective Raman operator

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• Breathers and Raman scattering in a two-leg ladder with staggered Dzialoshinskii-Moriya interaction
• Raman study of spin excitations in the tunable quantum spin ladder Cu(Qnx)(Cl${}_{1-x}$Br${}_x$)${}_2$
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• Theory of the Raman spectra of the Shastry-Sutherland antiferromagnet SrCu${}_2$(BO${}_3$)${}_2$ doped with nonmagnetic impurities
• Raman resonance in spin S two-leg ladder systems
• Resonant two-magnon Raman scattering in two-dimensional and ladder-type Mott insulators