Ultrafast and gigantic spin injection in semiconductors

TL;DR

This paper proposes a femtosecond laser-based method to inject highly polarized spin currents into semiconductors, enabling ultrafast spintronics with record polarization levels and femtosecond pulse durations.

Contribution

It introduces a novel ultrafast spin injection technique using laser-induced superdiffusive spin currents at ferromagnet-semiconductor interfaces, achieving record polarization.

Findings

Achieves 80% spin polarization in injected currents.

Pulsed injection on 100 femtosecond timescale.

Demonstrates a new ultrafast spintronics pathway.

Abstract

The injection of spin currents in semiconductors is one of the big challenges of spintronics. Motivated by the ultrafast demagnetisation and spin injection into metals, we propose an alternative femtosecond route based on the laser excitation of superdiffusive spin currents in a ferromagnet such as Ni. Our calculations show that even though only a fraction of the current crosses the Ni-Si interface, the laser-induced creation of strong transient electrical fields at a ferromagnet-semiconductor interface allows for the injection of chargeless spin currents with a record spin polarisations of 80%. Beyond that they are pulsed on the time scale of 100 femtoseconds which opens the door for new experiments and ultrafast spintronics.