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arXiv · 0808.3354

Sharp optical phonon softening close to optimal doping in La$_{2-x}$Ba$_x$CuO$_{4+δ}$

Matteo D'Astuto·Guy Dhalenne·Jeff Graf·Moritz Hoesch·Paola Giura·Michael Krisch·Patrick Berthet·Alessandra Lanzara·Abhay Shukla
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Abstract

We report a direct observation of a sharp Kohn-like anomaly in the doubly degenerate copper-oxygen bond-stretching phonon mode occurring at $\mathbf{q}\mathrm{=(0.3, 0,0)}$ in La$_{2-x}$Ba$_x$CuO$_{4+δ}$ with $\mathrm{x=0.14\pm0.01}$, thanks to the high $\mathbf{Q}$ resolution of inelastic x-ray scattering. This anomaly is clearly seen when the inelastic signal is analysed using a single mode but is also consistent with a two mode hypothesis possibly due to a splitting of the degenerate modes due to symmetry breaking stripes. Our observation shows that the effect persists at the stripe propagation vector in a superconducting system close to optimal doping.

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Matteo D'Astuto, Guy Dhalenne, Jeff Graf, Moritz Hoesch, Paola Giura, Michael Krisch, Patrick Berthet, Alessandra Lanzara, Abhay Shukla. 2008-10-01. Sharp optical phonon softening close to optimal doping in La$_{2-x}$Ba$_x$CuO$_{4+δ}$. https://doi.org/10.1103/physrevb.78.140511

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