Spin-dependent transport in a clean one-dimensional channel

A shoulderlike feature close to $(0.7\mathrm{}\times {2e}^2/h),$ “the 0.7 structure” at zero magnetic field was observed in clean one-dimensional (1D) channels [K.J. Thomas et al., Phys. Rev. Lett. 77, 135 (1996)]. To provide further understanding of this structure, we have performed low-temperature measurements of a 1D channel with overlaying finger gates to study the 0.7 structure as a function of lateral confinement strength and potential profile. We found that the structure persists when the lateral confinement strength is changed by a factor of 2. We have also shown that the 0.7 structure present in two 1D channels in series behaves like a single 1D channel that shows the 0.7 structure, demonstrating that the 0.7 structure is not a transmission effect through a ballistic channel at zero in-plane magnetic field.