Lattice-dynamical calculation of phonon scattering at a disordered interface

For an fcc crystal with central force interactions and separately for a scalar model on a square lattice, we compute exactly the phonon transmission coefficient $T(\omega)$ through a disordered planar interface between two identical semi - infinite leads. At high frequencies $T(\omega)$ exhibits a strong frequency dependence which is determined by the correlation length of the disorder.Comment: to appear in Physica B, proceedings of the 9th international conference on phonon scatterin

BACKWARD WAVE PHONON ECHOES AT 17 GHz IN SINGLE CRYSTALS OF LiTaO3, LiNbO3 AND Bi12SiO20

From measurements of the power and time dependence of ω- ω 2 pulse echoes at 17 GHz, we inferred that, at low powers, an intrinsic non-linearity γS2E2 was responsible for their generation in LiTaO3 and LiNbO3. However, this model could not explain either the high power data in these materials, or any of the results in Bi12SiO20

Experimental and theoretical response of distributed read-out imaging devices with imperfect charge confinement

Contains fulltext : 83621.pdf (publisher's version ) (Open Access

Efficiency of quasiparticle creation in proximized superconducting photon detectors

Contains fulltext : 75666.pdf (publisher's version ) (Open Access)7 p

Position dependent spatial and spectral resolution measurement of distributed readout superconducting imaging detectors

Contains fulltext : 72071.pdf (publisher's version ) (Open Access)10 p

Energy relaxation in a superconductor with magnetic impurities

In a superconductor with magnetic impurities, Kondo scattering results in the formation of localized states inside the superconducting gap. We show that inelastic electronic transitions involving quasiparticle scattering into and out of the localized states may result in significant changes in the non-equilibrium properties of the superconductor. Using the model of Muller-Hartmann and Zittartz for the extreme dilute limit, and including both deformation potential and spin-lattice coupling, we have calculated the rates of such inelastic transitions between continuum and discrete states, and shown that they may greatly modify quasiparticle interactions. The individual processes are: quasiparticle trapping into discrete states, enhanced recombination with localized quasiparticles, and pair breaking and de-trapping of localized quasiparticles by sub-gap phonons. We find that all these processes give rise to clearly distinguishable temperature dependences of the kinetic parameters

MEASUREMENT OF ENERGY-LOSS FROM A HEMT STRUCTURE BY OBSERVING EMITTED PHONONS

Using nanosecond heat pulse techniques we have observed both acoustic and optic phonon emission by the hot 2DEG in GaAs/AlGaAs HEMT structures. Both transverse and longitudinal modes were detected in the optic regime but only transverse in the acoustic regime. The ability to vary carrier density allowed us to eliminate the effect of contact resistance and hence to determine absolutely the power level at which energy loss took place equally via acoustic and optic phonons. The figure obtained was 2.3 +/- 0.5 pW per electron, inconsistent with a model of acoustic emission based simply on deformation potential coupling, suggesting the presence of an additional source of inelastic scattering