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.
@article{arxiv.2110.01486,
title = {All-optical spin injection in silicon revealed by element specific time-resolved Kerr effect},
author = {Simone Laterza and Antonio Caretta and Richa Bhardwaj and Roberto Flammini and Paolo Moras and MatteoJugovac and Piu Rajak and Mahabul Islam and Regina Ciancio and Valentina Bonanni and Barbara Casarin and Alberto Simoncig and Marco Zangrando and Primoz Rebernik Ribic and Giuseppe Penco and Giovanni De Ninno and LucaGiannessi and Alexander Demidovich and Miltcho Danailov and Fulvio Parmigiani and Marco Malvestuto},
journal= {arXiv preprint arXiv:2110.01486},
year = {2021}
}