Amplification of spin-filtering effect by magnetic field in GaAsN alloys

TL;DR

This study demonstrates that applying a magnetic field significantly enhances spin polarization and photoluminescence intensity in GaAsN alloys at room temperature, with effects influenced by pump intensity and possibly caused by hyperfine interactions.

Contribution

The paper introduces a two-charge-state model incorporating magnetic suppression of spin relaxation, explaining the magnetic field effects on spin polarization and luminescence in GaAsN alloys.

Findings

Magnetic field increases photoluminescence intensity and polarization by up to twofold.

Experimental shifts in magnetic response are attributed to the Overhauser field from hyperfine interactions.

Model qualitatively reproduces the magnetic field dependence of spin-related properties.

Abstract

We have found that intensity $I$ and circular polarization degree $\rho$ of the edge photoluminescence, excited in GaAsN alloys by circularly polarized light at room temperature, grow substantially in the longitudinal magnetic field $B$ of the order of 1\,kG. This increase depends on the intensity of pumping and, in the region of weak or moderate intensities, may reach a twofold value. In two-charge-state model, which considers spin-dependent recombination of spin-oriented free electrons on deep paramagnetic centers, we included the magnetic-field suppression of spin relaxation of the electrons bound on centers. The model describes qualitatively the rise of $\rho$ and $I$ in a magnetic field under different pump intensities. Experimental dependences $\rho(B)$ and $I(B)$ are shifted with respect to zero of the magnetic field by a value of $\sim$170\,Gauss, while the direction of the shift reverses with change of the sign of circular polarization of pumping. As a possible cause of the discovered shift we consider the Overhauser field, arising due to the hyperfine interaction of an electron bound on a center with nuclei of the crystal lattice in the vicinity of the center.