ISSN:
1432-0630
Keywords:
74
Source:
Springer Online Journal Archives 1860-2000
Topics:
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
,
Physics
Notes:
Abstract The experimental recombination lifetime τeff of quasiparticles in superconducting films in general exceeds the intrinsic recombination lifetime τ R 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 thicknessd taking into account longitudinal and transverse phonon reabsorption, bulk loss processes and acoustical phonon transmission into the substrate. With increasing thicknessd three characteristic ranges are found: range 1 with film thicknessd small compared to the phonon reabsorption mean free path Λ w range 2 withd larger than Λ w and dominating boundary losses, and range 3, also withd larger than Λ w but with dominating bulk losses. For very smalld the relation between τeff and τ R , the intrinsic recombination lifetime, contains only the limiting angle of total reflection of phonons within the superconducting film. Therefore, τ R can be directly obtained by τ eff measurements and from the sound velocities of the film-substrate system. Range 2 is characterized by a linear dependence of τ eff ond. In this range it is not possible to obtain τ R from τ eff measurements, however, τ eff allows a determination of the phonon boundary transmission. Range 3 shows no thickness dependence of τ eff ond in the limit of larged values. In this range a further method for obtaining τ R from τ eff values is suggested.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00919359
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