Study of spin-splitting in one-dimensional systems by magneto-capacitance measurements

We study the behavior of 1D systems in GaAs/AlGaAs hetero¬structures, whose filling is controlled by field effect. The confining poten¬tial is defined by fork-shaped interdigital metallic gates having lithogra-phic width ~150 nm. Measurement of the sample differential capa¬citance enable us to control the filling of single 1D subbands and investigate the thermodynamic and the tunneling DOS. The development of a structure related to spin splitting is studied as a function of both magnetic field and confinement. At the lowest 1D confinements, we find an enhanced g-fac¬tor g?15, which is a factor 35 larger than the "bare" value g=-0.44 for con¬duction band electrons in bulk GaAs. With increasing confinement, the g-factor is progressively suppressed. The observations are explained by theoretical models in terms of competition between exchange interactions and kinetic energy of edge electrons.