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With the advent of semiconductor spintronics, spin-polarized electron–hole plasmas could occur in semiconductors, leading to spin-dependent many-body effects. To understand these many-body effects, spin-dependent bandgap renormalization (BGR) often needs to be calculated quantitatively, which requires to know the fractional contribution of electrons (k) to the total BGR induced by the electron–hole plasma. However, the measurement of the k value is challenging because BGR is usually submerged or partially offset by the strong band-filling effect. Facing this challenge, we develop a new experimental technique which could measure spin-dependent many-body effects without the influence from the band-filling effect. The presented technique is employed in intrinsic bulk GaAs, with a dynamic model developed to extract the k value from the measured data. It is found that the k value in bulk GaAs increases with increasing concentration of the photoinjected electron–hole plasma but is consistently much less than the reported value in GaAs quantum wells. These results reveal obviously different many-body interactions in bulk GaAs and its quantum wells. [ABSTRACT FROM AUTHOR]

Transition metal-free half-metallicity recently has been the subject of intense research activity due to its potential in spintronics application. By employing density functional theory calculations, we revealed that F-intercalated GaN bilayers exhibit robust p orbital-based half-metallicity against the intercalant concentration and biaxial strain of −10% to 10%. The stable half-metallicity results from a spontaneous phase transition through Stoner instability and can be attributed to unusually high density of states near the Fermi level due to the quasi-flat bands. These findings provide a strategy to design transition-metal free half-metallic materials for futuristic spintronic applications. [ABSTRACT FROM AUTHOR]