Search results for "Phonon scattering"
showing 5 items of 35 documents
Second-order Raman scattering in CuO
2013
Polarized second-order Raman scattering spectra of CuO single crystals are reported. It is shown that for some scattering geometries the second-order processes dominate the inelastic light scattering spectra. Group-theoretical symmetry analysis of the selection rules for the first- and second-order scattering processes is performed and phonon dispersion relations are calculated within density functional theory. The main spectral features of the two-phonon spectra are assigned to overtones of the vibrational branches at various special points across the Brillouin zone.
Experimental studies of the liquid-glass transition in trimethylheptane
2000
The molecular glass former trimethylheptane was studied by calorimetric, dielectric, ultrasonic, neutron scattering, Brillouin scattering, and depolarized light-scattering techniques. The molecular structure appears to be nearly spherical optically as indicated by the low depolarization ratio and dielectric susceptibility values. A preliminary mode-coupling theory (MCT) analysis of the light-scattering and neutron-scattering data indicates that ${T}_{C}\ensuremath{\gtrsim}150 \mathrm{K},$ at least 25 K above ${T}_{G}.$ The susceptibility minima were analyzed with the MCT interpolation equation, and disagreement between the light and neutron results was observed despite the apparent isotropy…
Bag Scattering Theory
1986
We reanalyze the procedure used thus far for the study of collision processes in the Chiral Bag Model from the point of view of scattering theory. In the present formalism thein andout states are free waves with no memory of the cavity. This feature gives rise to an observable effect consisting in a peculiar momentum dependence of the scattering amplitudes, which differs from that of previous calculations. The new procedure however does not change the magnitude of the pion-baryon coupling constants.
Effects of quantum statistics of phonons on the thermal conductivity of silicon and germanium nanoribbons.
2012
: We present molecular dynamics simulation of phonon thermal conductivity of semiconductor nanoribbons with an account for phonon quantum statistics. In our semiquantum molecular dynamics simulation, dynamics of the system is described with the use of classical Newtonian equations of motion where the effect of phonon quantum statistics is introduced through random Langevin-like forces with a specific power spectral density (color noise). The color noise describes interaction of the molecular system with the thermostat. The thermal transport of silicon and germanium nanoribbons with atomically smooth (perfect) and rough (porous) edges are studied. We show that the existence of rough (porous)…
A Composite Phononic Crystal Design for Quasiparticle Lifetime Enhancement in Kinetic Inductance Detectors
2020
A nanoscale phononic crystal filter (reflector) is designed for a kinetic inductance detector where the reflection band is matched to the quasiparticle recombination phonons with the aim to increase quasiparticle lifetime in the superconducting resonator. The inductor is enclosed by a 1-μm-wide phononic crystal membrane section with two simple hole patterns that each contain a partial spectral gap for various high-frequency phonon modes. The phononic crystal is narrow enough for low-frequency thermal phonons to propagate unimpeded. With 3D phonon scattering simulation over a 40 dB attenuation in transmitted power is found for the crystal, which is estimated to give a lifetime enhancement of…