Enhancing spin diffusion in GaAs quantum wells: The role of electron density and channel width

Abstract

This study explores the relationship between spin diffusion, spin lifetime, electron density, and lateral spatial confinement in two-dimensional electron gases hosted in GaAs quantum wells. Using time-resolved magneto-optical Kerr effect microscopy, we analyze how Hall-bar channel width and back-gate voltage modulation influence spin dynamics. The results reveal that the spin diffusion coefficient increases with reduced channel widths, a trend further amplified at lower electron concentrations achieved via back-gate voltages, where it increases up to 150% for the narrowest channels. The theoretical model developed in this work suggests that the spin diffusion coefficient is spatially inhomogeneous across the channel cross section. Near the channel edges, where the electron density is reduced, the spin diffusion coefficient is enhanced due to weaker electron–electron scattering. As a result, narrower channels, which contain a relatively larger proportion of these low-density edge regions, exhibit overall faster spin diffusion. Our results underscore the importance of tuning electron density and spatial geometry to optimize spin transport and coherence, providing valuable design considerations for spintronic devices where efficient spin manipulation is crucial.