Publication

The broad Brillouin doublets and central peak of KTaO3

Alexander Tagantsev
2000
Journal Articles

Abstract

The incipient ferroelectric KTaO3 presents low-T Brillouin spectra anomalies, e.g. a broad central peak (CP), and some additional Brillouin doublets (BD). whose origin are interpreted in terms of phonon-density fluctuation processes. A parameterisation from new extensive high-resolution neutron-scattering measurements is used to show that hydrodynamic second sound from high damping (compared to ED frequency). TA phonons may exist in the crystal. Furthermore, low damping thermal phonons may scatter light through two-phonon difference processes and appear on Brillouin spectra either as a sharp or a broader ED, depending on the phonon damping and group velocity The comparison between computed anisotropies and experimental measurements favours the second process. (C) 2000 Elsevier Science B.V. All rights reserved.

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https://infoscience.epfl.ch/entities/publication/22b9bb30-667b-4df4-8299-b52a51ad3aa0

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Alexander Tagantsev
2000
Journal Articles

Abstract

Official source

https://infoscience.epfl.ch/entities/publication/22b9bb30-667b-4df4-8299-b52a51ad3aa0

About this result

Related concepts (32)

Electric-field screening

In physics, screening is the damping of electric fields caused by the presence of mobile charge carriers. It is an important part of the behavior of charge-carrying fluids, such as ionized gases (classical plasmas), electrolytes, and charge carriers in electronic conductors (semiconductors, metals). In a fluid, with a given permittivity ε, composed of electrically charged constituent particles, each pair of particles (with charges q1 and q2) interact through the Coulomb force as where the vector r is the relative position between the charges.

Scattering

Scattering is a term used in physics to describe a wide range of physical processes where moving particles or radiation of some form, such as light or sound, are forced to deviate from a straight trajectory by localized non-uniformities (including particles and radiation) in the medium through which they pass. In conventional use, this also includes deviation of reflected radiation from the angle predicted by the law of reflection.

Group velocity

The group velocity of a wave is the velocity with which the overall envelope shape of the wave's amplitudes—known as the modulation or envelope of the wave—propagates through space. For example, if a stone is thrown into the middle of a very still pond, a circular pattern of waves with a quiescent center appears in the water, also known as a capillary wave. The expanding ring of waves is the wave group or wave packet, within which one can discern individual waves that travel faster than the group as a whole.

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The broad Brillouin doublets and central peak of KTaO3

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