Portal de Periódicos da CAPES

Gapless phasons and transverse sound-wave asymmetries in K 2 SeO 4 </mml:mrow…

1987; American Physical Society; Volume: 36; Issue: 10 Linguagem: Inglês

10.1103/physrevb.36.5377

1095-3795

R. J. Gooding, M. B. Walker,

Crystal Structures and Properties

Based on an inelastic neutron scattering experiment, it has recently been suggested that phasons in the incommensurate phase of ${\mathrm{K}}_{2}$${\mathrm{SeO}}_{4}$ possess a gap of approximately 50 GHz [M. Quilichini and R. Currat, Solid State Commun. 48, 1011 (1983)]. We have found that these data may also be explained using a coupled phason sound-wave theory, for which the phasons are gapless. We then use the coupled excitation theory to predict certain velocity and attenuation asymmetries for transverse sound waves under interchange of their propagation and polarization directions. Lastly, we find that, in the long-wavelength limit, the attenuation asymmetry present for a system with gapless phasons is absent for a system possessing a phason gap.