Semiconductor nanowires: Tracing spin relaxation into the one-dimensional quantum regime

Being able to control the dimensionality of semiconductor devices is a key ingredient of many quantum technology concepts. While a broad spectrum of two- or zero-dimensional semiconductor systems have been successfully established, the realization of quantum-confined one-dimensional (1D) semiconductors is much more challenging. Consequently, for example, experimental investigations of the properties of spins in 1D nanostructures have been rare.
In this contribution, we systematically explore the fundamental characteristics of carriers in semiconductor nanowires all the way from a bulk-like environment down to clear 1D quantum confinement. In particular, we experimentally demonstrate that the relaxation time of an optically injected spin polarization increases by more than two orders of magnitude as we enhance the spatial confinement of the carriers. This increasing confinement is realized in catalytically grown wurtzite GaAs nanowires by epitaxially controlling the nanowire diameter down to ultrathin wires. We find the spin relaxation times in GaAs to exceed 200 ns when spatially squeezing the carriers into 1D quantum structures, demonstrating a clear transition in the spin relaxation physics.