Possible Spin Polarization in a One-Dimensional Electron Gas.

In zero magnetic field, conductance measurements of clean one-dimensional (1D) constrictions defined in GaAs/AlGaAs heterostructures show twenty-six quantized ballistic plateaux, as well as a structure close to 0.7(2e 2 /h). In an in-plane magnetic field all the 1D subbands show Zeeman splitting and in the wide channel limit the g-factor is | g |= 0.4, close to that of bulk GaAs. For the last subband spin-splitting originates from the structure at 0.7(2e 2 /h), indicating spin polarization at B = 0. The measured enhancement of the g-factor as the subbands are depopulated suggests that the " 0.7 structure " is induced by electron-electron interactions.