Injection of nonequilibrium quasiparticles into Zeeman-split superconductors: a way to create long-range spin imbalance

Abstract

A theory of spin transport and spin detection in Zeeman-split superconducting films at low temperatures is developed. It is shown that an injection of spin-unpolarized quasiparticles into a Zeeman-split superconductor gives rise to a spin imbalance. The relaxation length of such a spin signal is determined by the energy relaxation length and can be extremely large as compared to the relaxation length of spin-polarized quasiparticles. There can exist two types of signals: due to nonthermalized quasiparticle distribution and due to thermalized overheated electron distribution. They have different decay lengths and can be distinguished by their different dependencies on the applied voltage. The decay length of the nonthermalized signal is determined by the electron-electron scattering rate, renormalized due to superconductivity. The decay length of the thermalized signal is determined by the length on which energy leaves the electronic subsystem and can be very large under special conditions. Applications of the theory to recent experimental data on spin relaxation in Zeeman-split and exchange-split superconductors are discussed. In particular, it can explain the extremely high spin relaxation lengths, experimentally observed in Zeeman-split superconductors, and their growth with the magnetic field and with the applied voltage.

13 pages, 7 figures

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Cited by in corpus (13)

• Colloquium: Nonequilibrium effects in superconductors with a spin-splitting field
• Thermal, electric and spin transport in superconductor/ferromagnetic-insulator structures
• Thermoelectric effects in superconductor-ferromagnet tunnel junctions on europium sulfide
• Voltage-induced thin-film superconductivity in high magnetic fields
• Nonlocal thermoelectric effects in high-field superconductor-ferromagnet hybrid structures
• Thermospin effects in superconducting heterostructures
• Spin currents driven by the Higgs mode in magnetic superconductors
• Controlling spin supercurrents via nonequilibrium spin injection
• Paramagnetic Meissner effect in voltage-biased proximity systems
• Spin-polarized quasiparticle control in a double spin-filter tunnel junction
• Spin-dependent coupling of supercurrent and nonequilibrium quasiparticles in high-field superconductors
• Spin transport in a normal meta-altermagnetic superconducting nanowire junction
• Evidence for spin-dependent energy transport in a superconductor