Electron-nuclear spin dynamics of Ga$^{2+}$ paramagnetic centers probed by spin dependent recombination: A master equation approach

摘要

Similar to nitrogen-vacancy centers in diamond and impurity atoms in silicon,interstitial gallium deep paramagnetic centers in GaAsN have been proven tohave useful characteristics for the development of spintronic devices. Amongother interesting properties, under circularly polarized light, gallium centersin GaAsN act as spin filters that dynamically polarize free and bound electronsreaching record spin polarizations (100\%). Furthermore, the recent observationof the amplification of the spin filtering effect under a Faraday configurationmagnetic field has suggested that the hyperfine interaction that couples boundelectrons and nuclei permits the optical manipulation of its nuclear spinpolarization. Even though the mechanisms behind the nuclear spin polarizationin gallium centers are fairly well understood, the origin of nuclear spinrelaxation and the formation of an Overhauser-like magnetic field remainelusive. In this work we develop a model based on the master equation approachto describe the evolution of electronic and nuclear spin polarizations ofgallium centers interacting with free electrons and holes. Our results are ingood agreement with existing experimental observations. In regard to thenuclear spin relaxation, the roles of nuclear dipolar and quadrupolarinteractions are discussed. Our findings show that, besides the hyperfineinteraction, the spin relaxation mechanisms are key to understand theamplification of the spin filtering effect and the appearance of theOverhauser-like magnetic field. Based on our model's results we propose anexperimental protocol based on time resolved spectroscopy. It consists of apump-probe photoluminescence scheme that would allow the detection and thetracing of the electron-nucleus flip-flops through time resolved PLmeasurements.