Xiaoxiang Xi, J. Hwang, C. Martin, D. H. Reitze, C. J. Stanton, D. B. Tanner, G. L. Carr
Quasiparticle recombination in a full-gap superconductor is typically dominated by a phonon bottleneck effect. We have studied how a magnetic field changes this recombination process in conventional s-wave thin film superconductors, finding that the quasiparticle recombination process is significantly slowed by the field. While we observe this for all field orientations, we focus here on the results for a field applied parallel to the thin film surface, minimizing the influence of vortices. The magnetic field disrupts the time-reversal symmetry of the pairs, giving them a finite lifetime and decreasing the energy gap. The field could also polarize the quasiparticle spins, producing different populations of spin-up and spin-down quasiparticles. Both processes favor slower recombination; in our materials we conclude that strong spin-orbit scattering reduces the spin polarization, making gap reduction dominate.
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http://arxiv.org/abs/1211.3325
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