We report momentum-resolved charge excitations in a one-dimensional (1D) Mott insulator studied using high resolution inelastic x-ray scattering over the entire Brillouin zone for the first time. Excitations at the insulating gap edge are found to be highly dispersive (momentum dependent) compared to excitations observed in two-dimensional Mott insulators. The observed dispersion in 1D cuprates ( SrCuO2 and Sr2CuO3) is consistent with charge excitations involving holons which is unique to spin-1/2 quantum chain systems. These results point to the potential utility of momentum-resolved inelastic x-ray scattering in providing valuable information about electronic structure of strongly correlated insulators.
The Rapid Communications section is intended for the accelerated publication of important new results. Since manuscripts submitted to this section are given priority treatment both in the editorial ofhce and in production, authors should explain in their submittal letter why the work justifies this special handling A. Rapid Communication should be no longer than 3' printed pages and must be accompanied by an abstract. Page proofs are sent to authors, but, because of the accelerated schedule, publication is not delayed for receipt of corrections unless requested by the author or noted by the editor Effect of the electron mean free path in small particles on the extended x-ray-absorption Sne-structure determination of coordination nusssbers The transferability of the electron mean-free-path (MFP) value from the bulk standard to small particles is a standard procedure in the analysis of extended x-ray-absorption fine-structure (EXAFS) measurements. In this paper we show, using a simple example, that transferability of the MFP can lead to an incorrect evaluation of the coordination number. The electron MFP in small particles can be significantly different from the bulk. We illustrate this point by evaluating
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