All-optical spin injection in silicon revealed by element specific time-resolved Kerr effect

TL;DR

This study demonstrates direct detection of ultrafast spin currents across a Ni/Si interface using element-specific Kerr spectroscopy, revealing a propagation velocity of approximately 0.2 nm/fs in silicon, advancing ultrafast spintronics understanding.

Contribution

The paper introduces a novel element-specific Kerr spectroscopy technique to directly observe spin current propagation at femtosecond timescales in metal-semiconductor interfaces.

Findings

Direct evidence of spin currents across Ni/Si interface.

Measured spin current propagation velocity of ~0.2 nm/fs in silicon.

Utilized free electron laser-based element sensitive Kerr spectroscopy.

Abstract

Understanding how a spin current flows across metal-semiconductor interfaces at pico- and femtosecond timescales has implications for ultrafast spintronics, data processing and storage applications. However, the possibility to directly access the propagation of spin currents on such time scales has been hampered by the simultaneous lack of both ultrafast element specific magnetic sensitive probes and tailored metal-semiconductor interfaces. Here, by means of free electron laser-based element sensitive Kerr spectroscopy, we report direct experimental evidence of spin currents across a Ni/Si interface in the form of different magnetodynamics at the Ni M2,3 and Si L2,3 absorption edges. This further allows us to calculate the propagation velocity of the spin current in silicon, which is on the order of 0.2 nm/fs.