Spin-dependent transport in a quasiballistic quantum wire

We describe the transport properties of a $5-\mu \mathrm{m}$-long one-dimensional (1D) quantum wire. Reduction of conductance plateaus due to the introduction of weak disorder scattering is observed. In an in-plane magnetic field, we observe a spin splitting of the reduced conductance steps. Our experimental results provide evidence that the deviation from conductance quantization is very small for electrons with spin parallel and is about $1/3$ for electrons with spin antiparallel. Moreover, in a high in-plane magnetic field, a spin-polarized 1D channel shows a plateaulike structure close to ${0.3e}^2/h$ which strengthens with increasing temperature. It is suggested that these results arise from a combination of disorder and electron-electron interactions in a 1D electron gas.