Abstract

The spin of charge carriers provides an additional degree of freedom to charge for storing and processing information. One avenue for achieving such control of spin is through the phenomenon of spin-orbit coupling in low dimensional hole based GaAs heterostructures. Due to the strong spin-orbit interaction in the valence band, spatially confining holes in these heterostructures also influences spin. For example it has been theoretically predicted that for heavy holes confined to a 2D plane in (100) GaAs, the effective Lande g-factor g = 0 for an in-plane field, but g = 7.2 for an out-of-plane field. This large anisotropy of the Landé g-factor for holes in GaAs has been established theoretically for over two decades. However, despite numerous attempts over the past 20 years, no reported experiment has yet been able to measure a value close to the predicted g-factor of g =7.2. In this work we attempt to corroborate the long standing theory by directly measuring g electrically. However measuring the Zeeman splitting in 2D systems is not possible, as there are no spectroscopic tools available. Instead we use a 1D wire, and investigate the limiting behaviour as it becomes two-dimensional. The quantum wire allows us to perform energy spectroscopy and directly observe the Zeeman splitting as a function of magnetic field. We find a large anisotropy (g_perp/g|| > 5) in agreement with theoretical expectations. For n=5, we measure g ~ 5, which is approaching the theoretical 2D limit of 7.2.