The extra brillouin doublets and central peak of KTaO3: Second sound vs. two-phonon difference scattering
Low-T Brillouin spectra of the incipient ferroelectric KTaO3 exhibit a broad central peak (CP), and additional Brillouin doublets (BD), that can both be related to phonon-density fluctuations. On the basis of new high-resolution neutron data obtained of low-lying phonon branches, we analysed the phonon-kinetics mechanisms that are possibly the origin of these unusual features. Firstly, transverse acoustic (TA) phonons whose normal damping is faster than the ED frequency can produce hydrodynamic second sound. Secondly, two-phonon difference scattering from low damping thermal transverse phonons contribute to the spectra with either a sharp or a broader doublet, depending on the phonon group velocity and anisotropy of dispersion surfaces. The position of the observed sharp doublet is consistent with both mechanisms, but a comparison of the computed and experimental anisotropies favours the second process.
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Farhi, E Univ Montpellier 2, Lab Verres, F-34095 Montpellier, France Univ Montpellier 2, Lab Verres, F-34095 Montpellier, France Inst Max Von Laue Paul Langevin, F-38042 Grenoble 9, France EPFL, Lab Ceram, CH-1015 Lausanne, Switzerland Oak Ridge Natl Lab, Div Solid State, Oak Ridge, TN 37831 USA
Cited References Count:27
Record created on 2006-08-21, modified on 2016-08-08