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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 0ex{0ex}=0ex{0ex}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 B0ex{0ex}=0ex{0ex}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.
Thomas et al. (Mon,) studied this question.