NONLINEAR TRANSPORT IN A SINGLE-MODE ONE-DIMENSIONAL ELECTRON-GAS

Focusing on the last spin-degenerate one-dimensional subband, conducta nce measurements of split-gate devices were carried out in the linear and nonlinear regimes. In the linear regime, we observed a structure a t 0.7(2e(2)/h) in addition to the quantized plateaux. In a strong in-p lane magnetic field B this 0.7 structure evolves into the spin-split p lateau at e(2)/h, suggesting a possible spin polarization for the last subband at B = 0. The 0.7 structure and the e(2)/h plateau show simil ar source-drain bias dependence, suggesting that the 0.7 structure has origin in the lower spin subband.