What happens to spin-polarised electrons when they enter a superconductor ? Superconductors at equilibrium and at finite temperature contain both paired particles (of opposite spin) in the condensate phase as well as unpaired, spin-randomised quasiparticles. Injecting spin-polarised electrons into a superconductor thus creates both spin and charge imbalances. These must relax when the injection stops, but not necessarily over the same timescale. These different relaxation times can be probed by creating a dynamic equilibrium between continuous injection and relaxation, which leads to constant-in-time spin and charge imbalances. These scale with their respective relaxation times and with the injection current. Spin-charge separation effects could occur e.g. if the spin relaxation time is longer than the charge relaxation time. In a recent article published in Nature Physics [1], C. Bena et al. present evidence for an almost-chargeless spin imbalance in a mesoscopic superconductor.

[1] C. H. L. Quay,  D. Chevallier,  C. Bena &  M. Aprili, Nature Physics 9, 84-88 (2013).