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arXiv · 0709.3274

Observation of a 500meV Collective Mode in La$_{2-x}$Sr$_x$CuO$_4$ and Nd$_2$CuO$_4$

J. P. Hill·G. Blumberg·Young-June Kim·D. Ellis·S. Wakimoto·R. J. Birgeneau·Seiki Komiya·Yoichi Ando·B. Liang·R. L. Greene·D. Casa·T. Gog
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Abstract

Utilizing resonant inelastic x-ray scattering, we report a previously unobserved mode in the excitation spectrum of La$_{2-x}$Sr$_x$CuO$_4$ at 500 meV. The mode is peaked around the ($π$,0) point in reciprocal space and is observed to soften, and broaden, away from this point. Samples with x=0, 0.01, 0.05, and 0.17 were studied. The new mode is found to be rapidly suppressed with increasing Sr content and is absent at $x$=0.17, where it is replaced by a continuum of excitations. The peak is only observed when the incident x-ray polarization is normal to the CuO planes and is also present in Nd$_2$CuO$_4$. We suggest possible explanations for this excitation.

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J. P. Hill, G. Blumberg, Young-June Kim, D. Ellis, S. Wakimoto, R. J. Birgeneau, Seiki Komiya, Yoichi Ando, B. Liang, R. L. Greene, D. Casa, T. Gog. 2007-09-20. Observation of a 500meV Collective Mode in La$_{2-x}$Sr$_x$CuO$_4$ and Nd$_2$CuO$_4$. https://doi.org/10.1103/physrevlett.100.097001

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