Possible Spin Polarization in a One-Dimensional Electron Gas

Abstract

In zero magnetic field, conductance measurements of clean one-dimensional (1D) constrictions defined in GaAs/AlGaAs heterostructures show up to 26 quantized ballistic plateaus, as well as a structure close to $0.7({2e}^2/h)$. In an in-plane magnetic field all the 1D subbands show linear Zeeman splitting, and in the wide channel limit the $g$ factor is $\mid g\mid =0.4\mathrm{}$, 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 $B=0\mathrm{}$. The measured enhancement of the $g$ factor as the subbands are depopulated suggests that the “0.7 structure” is induced by electron-electron interactions.