Long-range spin imbalance in mesoscopic superconductors under a Zeeman splitting
I. V. Bobkova+*, A. M. Bobkov+
+Institute of Solid State Physics, 142432 Chernogolovka, Russia
*Moscow Institute of Physics and Technology, 141700 Dolgoprudny, Russia
Abstract
We develop a theory of spin relaxation in Zeeman-splitted
superconducting films at low temperatures. A new mechanism of spin relaxation,
specific only for Zeeman-splitted superconductors is proposed. It can explain
the extremely high spin relaxation lengths, experimentally observed in
Zeeman-splitted superconductors, and their strong growth with the magnetic field. In
the framework of this mechanism the observed spin signal is formed by the
spin-independent nonequilibrium quasiparticle distribution weighted by the spin-split
DOS. We demonstrate that the relaxation length of such a spin signal is
determined by the energy relaxation length at energies of the order of the
superconducting gap.