Calculation of the order-parameter relaxation times in superconducting aluminum

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Abstract
A calculation of the electron-phonon-limited quasiparticle lifetimes in aluminum, which is accurate for temperatures down to absolute zero, is used to evaluate the characteristic relaxation times of the order parameter just below the superconducting transition. The large anisotropy of the quasiparticle lifetimes is discussed, and the appropriate average (i.e., the average of the inverse lifetimes) is taken for the evaluation of the superconducting times. The calculation is used as a vehicle for comparing the measured lifetimes of the superconducting phase with those of the normal phase. The overall agreement is quite good, although some of the superconducting samples exhibit times shorter than what one would expect on the basis of the theoretical relationships derived by Schmid and Schön. We discuss the possibility of attributing this to certain other relaxation mechanisms, such as electron-electron scattering.