Quasiparticle Spin Resonance and Coherence in Superconducting Aluminium

Abstract

Spin/magnetisation relaxation and coherence times, respectively T_1 and T_2, initially defined in the context of nuclear magnetic resonance (NMR), are general concepts applicable to a wide range of systems, including quantum bits [1-4]. At first glance, these ideas might seem to be irrelevant to conventional Bardeen-Cooper-Schrieffer (BCS) superconductors, as the BCS superconducting ground state is a condensate of Cooper pairs of electrons with opposite spins (in a singlet state) [5]. It has recently been demonstrated, however, that a non-equilibrium magnetisation can appear in the quasiparticle (i.e. excitation) population of a conventional superconductor, with relaxation times on the order of several nanoseconds [6-10]. This raises the question of the spin coherence time of quasiparticles in superconductors and whether this can be measured through resonance experiments analogous to NMR and electron spin resonance (ESR). We have performed such measurements in aluminium and find a quasiparticle spin coherence time of 95+/-20ps.

12 pages, 3 figures + Supp. Info

References in corpus (9)

• Driven coherent oscillations of a single electron spin in a quantum dot
• Superconducting Spintronics
• Number fluctuations of sparse quasiparticles in a superconductor
• 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 and relaxation in a mesoscopic superconductor
• Long-range spin and charge accumulation in mesoscopic superconductors with Zeeman splitting
• Spin injection from a normal metal into a mesoscopic superconductor
• Non-equilibrium spin transport in Zeeman-split superconductors

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• Flux flow spin Hall effect in type-II superconductors with spin-splitting field
• Stimulated quasiparticles in spin-split superconductors
• Out-of-Equilibrium Spin Transport in Mesoscopic Superconductors
• Breakdown of the Hebel-Slichter effect in superconducting graphene due to the emergence of Yu-Shiba-Rusinov states at magnetic resonant scatterers
• Clocked single-spin source based on a spin-split superconductor
• Spin relaxation, Josephson effect and Yu-Shiba-Rusinov states in superconducting bilayer graphene
• Spin-polarized quasiparticle control in a double spin-filter tunnel junction
• Evidence for spin-dependent energy transport in a superconductor