Boson peak in overdoped manganites La_{1-x}Ca_{x}MnO_{3}

In the charge-ordered phase of strongly doped manganites La\(_{1-x}\)Ca\(_x\)MnO\(_3\) (\(x \geq 0.5\)) absorption lines appear in the terahertz spectral range for commensurate \(x\) values right below the charge-ordering temperature. They are connected to acoustic phonons that become optically acti...

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Bibliographic Details
Published in:arXiv.org 2013-03
Main Authors: Gorshunov, B, Zhukova, E, Torgashev, V I, Kadyrov, L S, Motovilova, L, Fischgrabe, F, Zhang, V Moshnyaga T, Kremer, R, Pracht, U, Zapf, S, Dressel, M
Format: Article
Language:English
Subjects:
Absorption spectra
Brillouin zones
Calcium
Folding
Manganese oxides
Manganites
Optical activity
Phonons
Vibrational states
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Summary:In the charge-ordered phase of strongly doped manganites La\(_{1-x}\)Ca\(_x\)MnO\(_3\) (\(x \geq 0.5\)) absorption lines appear in the terahertz spectral range for commensurate \(x\) values right below the charge-ordering temperature. They are connected to acoustic phonons that become optically active by folding of the Brillouin zone. At lower temperatures a strongly asymmetric extra absorption band develops at frequencies corresponding to the position of the lowest-energy van Hove singularity in the reduced Brillouin zone. The band is assigned to the boson peak, i.e. to the excess of lattice vibrational states over the standard Debye contribution. The folded phonons and the boson peak do not show up for incommensurate calcium contents when no distinct Brillouin zone folding exists.
ISSN:2331-8422
DOI:10.48550/arxiv.1303.1992