Extremely long quasiparticle spin lifetimes in superconducting aluminium using MgO tunnel spin injectors

TL;DR

This study demonstrates that superconducting aluminum can host spin-polarized quasiparticles with extremely long lifetimes, vastly exceeding those in the normal state, with implications for spintronics and quantum computing devices.

Contribution

It provides the first quantitative measurement of long-lived spin-polarized quasiparticles in superconducting aluminum using MgO tunnel spin injectors.

Findings

Spin lifetimes in superconducting aluminum are nearly a million times longer than in the normal state.

The suppression of superconductivity correlates with the accumulation of spin-polarized quasiparticles.

Small electric currents can significantly modify the superconducting state, relevant for qubit devices.

Abstract

There has been an intense search in recent years for long-lived spin-polarized carriers for spintronic and quantum-computing devices. Here we report that spin polarized quasi-particles in superconducting aluminum layers have surprisingly long spin-lifetimes, nearly a million times longer than in their normal state. The lifetime is determined from the suppression of the aluminum's superconductivity resulting from the accumulation of spin polarized carriers in the aluminum layer using tunnel spin injectors. A Hanle effect, observed in the presence of small in-plane orthogonal fields, is shown to be quantitatively consistent with the presence of long-lived spin polarized quasi-particles. Our experiments show that the superconducting state can be significantly modified by small electric currents, much smaller than the critical current, which is potentially useful for devices involving superconducting qubits.