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arXiv · 1111.1914

Response of acoustic phonons to charge and orbital order in the 50\% doped bilayer manganite LaSr$_2$Mn$_2$O$_7$

F. Weber·S. Rosenkranz·J. -P. Castellan·R. Osborn·H. Zheng·J. F. Mitchell·Y. Chen·Songxue Chi·J. W. Lynn·D. Reznik
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Abstract

We report an inelastic neutron scattering study of acoustic phonons in the charge and orbitally ordered bilayer manganite LaSr$_2$Mn$_2$O$_7$. For excitation energies less than $15\,\rm{meV}$, we observe an abrupt increase (decrease) of the phonon energies (linewidths) of a transverse acoustic phonon branch at $\mathbf{q} = (h, h, 0)$, $h\le0.3$, upon entering the low temperature charge and orbital ordered state ($T_{COO} = 225\,\rm{K}$). This indicates a reduced electron-phonon coupling due to a decrease of electronic states at the Fermi level leading to a partial removal of the Fermi surface below $T_{COO}$ and provides direct experimental evidence for a link between electron-phonon coupling and charge order in manganites.

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F. Weber, S. Rosenkranz, J. -P. Castellan, R. Osborn, H. Zheng, J. F. Mitchell, Y. Chen, Songxue Chi, J. W. Lynn, D. Reznik. 2011-11-08. Response of acoustic phonons to charge and orbital order in the 50\% doped bilayer manganite LaSr$_2$Mn$_2$O$_7$. https://doi.org/10.1103/physrevlett.107.207202

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