H. Gretarsson, J. P. Clancy, Yogesh Singh, P. Gegenwart, J. P. Hill, Jungho Kim, M. H. Upton, A. H. Said, D. Casa, T. Gog, Young-June Kim
The low energy excitations in Na2IrO3 have been investigated using resonant inelastic x-ray scattering (RIXS). A magnetic excitation branch can be resolved, whose dispersion reaches a maximum energy of about 35 meV at the \Gamma-point. The momentum dependence of the excitation energy is much larger along the \Gamma-X direction compared to that along the \Gamma-Y direction. The observed dispersion relation is consistent with a recent theoretical prediction based on Heisenberg-Kitaev model. At high temperatures, we find large contributions from lattice vibrational modes to our RIXS spectra, suggesting that a strong electron-lattice coupling is present in Na2IrO3.
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http://arxiv.org/abs/1304.4484
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