Control of spin relaxation in GaAs nanowires with electric bias and nanowires aspect ratio

Motivated by the importance of understanding spin relaxation in semiconductor nanostructures, such as quantum dots and quantum wells, we studied how electric field and contact geometry controls spin relaxation in 1D nanowires. We report spin relaxation time in 50-400 ns range for a range of sample geometries and nanowire aspect ratio. Further, the range of applied voltages, of the order of 1V, and electric fields is technologically relevant. In our experiments, we have relied on spin noise spectroscopy applied to substrate supported back-etched nanowires. One unusual feature of the spin noise spectrum in our nanowires is an appearance of a secondary, satellite peak, in addition to the expected peak. Both, the main and the secondary peak bear similarities to the single peak spin noise spectra in quantum dots and quantum wells. We modeled these spectra using a modified spectral response function, and we propose this secondary peak appears due to a transition between two modes of spin transport within nanowires. Namely, depending on biasing condition, temperature, and geometry, our analysis suggests that spin noise spectra show signs of both drift-diffusion transport and ballistic transport.