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Optical spin pumping in silicon

Stefano Achilli1, Damiano Marian2, Mario Lodari3, Luca Moreschini3, Emiliano Bonera1, Giordano Scappucci3, Jacopo Pedrini1, Michele Virgilio2, and Fabio Pezzoli1,*

  • *Contact author: fabio.pezzoli@unimib.it
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Phys. Rev. Research 8, 023302 – Published 16 June, 2026

DOI: https://doi.org/10.1103/cdkm-m3qc

Abstract

The optical generation of an out-of-equilibrium spin population is a keystone process for quantum technologies and spintronics alike. Although this is an established technique for studying direct band-gap semiconductors, it has been proven limited in materials that possess weak oscillator strengths for the optical transitions. We address the problem by presenting an all-optical analog of the spin-pumping method. By applying this concept to a Ge-on-Si heterostructure, we observe luminescence from Si with a polarization degree as high as 9%. The progressive etching of the absorbing layer, assisted by magneto-optic experiments, allows us to ascertain that the polarized emission is determined by effective spin injection aided by the carrier lifetime shortening due to extended defects. These findings can facilitate the use of highly promising spin-dependent phenomena of Si, whose optical exploitation has been hampered by fundamental limitations due to its peculiar electronic structure.

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Phys. Rev. Research 8, 023302– Published 16 June, 2026
  • Received 19 December 2025
  • Accepted 9 May 2026
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Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.

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