Optical spin pumping in silicon
Stefano Achilli (Università degli Studi di Milano Bicocca)
Damiano Marian (University of Pisa)
Mario Lodari (Kavli institute of nanoscience Delft, TU Delft - QuTech Advanced Research Centre, TU Delft - QCD/Scappucci Lab)
Luca Moreschini (Kavli institute of nanoscience Delft, TU Delft - QCD/Scappucci Lab, TU Delft - QuTech Advanced Research Centre)
Emiliano Bonera (Università degli Studi di Milano Bicocca)
Giordano Scappucci (TU Delft - Electrical Engineering, Mathematics and Computer Science, Kavli institute of nanoscience Delft, TU Delft - QCD/Scappucci Lab, TU Delft - QuTech Advanced Research Centre)
Jacopo Pedrini (Università degli Studi di Milano Bicocca)
Michele Virgilio (University of Pisa)
Fabio Pezzoli (Università degli Studi di Milano Bicocca)
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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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