Boson peak in manganites

After the phase transition occurs in manganites La1-xCaxMnO3 (x ≥ 0.5) into a dielectric phase with charge order, right below the corresponding temperature of TCO = 240 K a series of absorption lines appear in the terahertz spectral range, only in case of commensurate x values. We show that the line...

Full description

Saved in:
Bibliographic Details
Published in:Journal of physics. Conference series 2014-01, Vol.486 (1), p.12001-2
Main Authors: Gorshunov, Boris P, Zhukova, Elena S, Torgashev, Victor I, Kadyrov, Lenar S, Motovilova, Elizaveta A, Fischgrabe, Florian, Moshnyaga, Vasiliy, Zhang, Tao, Kremer, Reinhard, Pracht, Uwe, Zapf, Sina, Dressel, Martin
Format: Article
Language:English
Subjects:
Absorption spectra
Bosons
Brillouin zone
Brillouin zones
Calcium
Charge
Manganites
Optical activity
Phase transformations
Phase transitions
Phonons
Physics
Vibrational states
Citations: Items that this one cites
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:After the phase transition occurs in manganites La1-xCaxMnO3 (x ≥ 0.5) into a dielectric phase with charge order, right below the corresponding temperature of TCO = 240 K a series of absorption lines appear in the terahertz spectral range, only in case of commensurate x values. We show that the lines originate from acoustic phonons that become optically active by folding of the Brillouin zone. At even lower temperatures, a strongly asymmetric extra absorption band develops at frequencies around 20 cm−1 – 30 cm−1 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.
ISSN:1742-6596
1742-6588
1742-6596
DOI:10.1088/1742-6596/486/1/012001