Frequency-Domain Measurement of the Spin Imbalance Lifetime in Superconductors

Abstract

We have measured the lifetime of spin imbalances in the quasiparticle population of a superconductor (${\tau }_s$) in the frequency domain. A time-dependent spin imbalance is created by injecting spin-polarised electrons at finite excitation frequencies into a thin-film mesoscopic superconductor (Al) in an in-plane magnetic field (in the Pauli limit). The time-averaged value of the spin imbalance signal as a function of excitation frequency, $f_{RF}$ shows a cut-off at $f_{RF}\approx 1/(2\pi {\tau }_s)$. The spin imbalance lifetime is relatively constant in the accessible ranges of temperatures, with perhaps a slight increase with increasing magnetic field. Taking into account sample thickness effects, ${\tau }_s$ is consistent with previous measurements and of the order of the electron-electron scattering time ${\tau }_{ee}$. Our data are qualitatively well-described by a theoretical model taking into account all quasiparticle tunnelling processes from a normal metal into a superconductor.

Includes Supplementary Information

References in corpus (5)

• Spin Imbalance and Spin-Charge Separation in a Mesoscopic Superconductor
• Long-range spin-polarized quasiparticle transport in mesoscopic Al superconductors with a Zeeman splitting
• Spin injection from a normal metal into a mesoscopic superconductor
• Separating pairing from quantum phase coherence dynamics above the superconducting transition by femtosecond spectroscopy
• Quasiparticle Spin Resonance and Coherence in Superconducting Aluminium

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