Tatsuya Nagao, Jun-ichi Igarashi
We study the magnetic excitation spectra of Cu L_{2,3}-edge resonant inelastic x-ray scattering (RIXS) from the spin-liquid ground state in two-leg spin ladder cuprates. Applying the projection method developed by the present authors, we have derived the formulas of the magnetic RIXS spectra, which are expressed by one- and two-spin correlation functions in the polarization changing and preserving channels, respectively. The one-spin correlation function includes both one- and two-triplon excitations and they are picked up separately by choosing rung wave vector -q_a=\pi and 0, respectively. An application to Sr_{14}Cu_{24}O_{41} reveals that the calculated RIXS spectrum captures well the dispersive behavior shown by the lower boundary of two-triplon continuum. By adjusting the geometrical configuration of the measurement, one-triplon dispersion around the zone center could be detectable in the RIXS experiment. The observed weak intensity in the higher energy region might be attributed to the two-spin correlation function, which could be detected more clearly at the M_{3}-edge RIXS spectra.
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http://arxiv.org/abs/1205.4069
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