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Item Open Access Quasiparticle recombination and 2Δ-phonon-trapping in superconducting tunnelling junctions(1976) Eisenmenger, Wolfgang; Lassmann, Kurt; Trumpp, Hans-Joachim; Krauß, RichardThe experimental recombination lifetime τeff of quasiparticles in superconducting films in general exceeds the intrinsic recombination lifetime τR by phonon trapping. On the basis of geometric acoustic propagation and reabsorption of phonons emitted in quasiparticle recombination, τeff is calculated as a function of film thickness d taking into account longitudinal and transverse phonon reabsorption, bulk loss processes and acoustical phonon transmission into the substrate. With increasing thickness d three characteristic ranges are found: range 1 with film thickness d small compared to the phonon reabsorption mean free path Λw, range 2 with d larger than Λw and dominating boundary losses, and range 3, also with d larger than Λw but with dominating bulk losses. For very small d the relation between τeff and τR, the intrinsic recombination lifetime, contains only the limiting angle of total reflection of phonons within the superconducting film. Therefore, τR can be directly obtained by τeff measurements and from the sound velocities of the film-substrate system. Range 2 is characterized by a linear dependence of τeff on d. In this range it is not possible to obtain τR from τeff measurements, however, τeff allows a determination of the phonon boundary transmission. Range 3 shows no thickness dependence of τeff on d in the limit of large d values. In this range a further method for obtaining τR from τeff values is suggested.Item Open Access Analysis of the acoustlc transients in the pulse response of the linear electro-optic effect(1976) Veeser, Hermann; Bogner, Udo; Eisenmenger, WolfgangThe pulse response of the linear electro-optic effect is investigated with high temporal and spatial resolution in KDP, KD*P, and biaxial LiCOOH · H2O. Experimental results, which are explained theoretically, show that the piezo-optic transients induced by the piezoelectric effect, are generated by stress release waves. Starting from the surfaces, these excite by reflection, diffraction, and superposition, due to the finite crystal dimensions, normal vibration modes too. It is shown that the direct electro-optic effect can be measured for all crystal classes at the beginning of the pulse response. The pulse method also yields static electro-optic, piezo-optic, and elastic constants. The values of r63, r63, p66 and c66 measured in KDP, agree well with those of other authors. Measurement of the direct electro-optic effect of LiCOOH · H2O in some directions yields values within 1 to 4 × 10-12 m/V.Item Open Access High frequency phonon emission from superconducting Al-tunnelling junctions(1976) Eisenmenger, WolfgangIn single particle tunneling between identical superconductors phonons are generated by relaxation - and recombination transitions of injected quasiparticles. Phonon detection is mediated by the breaking of Cooper-pairs by phonons with energy exceeding the superconducting energy gap 2Δ D. This leads to an increase of the quasiparticle population and a corresponding contribution to the tunneling current in the thermal tunneling regime 0Item Open Access Superconducting tunnelling junctions as phonon generators and detectors(1976) Eisenmenger, WolfgangIt is the aim of this chapter to review the experimental and theoretical results obtained by the use of superconducting tunneling junctions as phonon generators and detectors. We first discuss the fundamental processes and their experimental evidence in more qualitative terms in Sections II and III. The quantitative treatment of phonon detection and generation is given in Sections IV and V, while Section VI discusses phonon spectroscopy and other applications.