Spin-Incoherent Transport in Quantum Wires

When a quantum wire is weakly confined, a conductance plateau appears at $e^2/h$ with decreasing carrier density in zero magnetic field accompanied by a gradual suppression of the $2e^2/h$ plateau. Applying an in-plane magnetic field $B_{\parallel }$ does not alter the value of this quantization; however, the $e^2/h$ plateau weakens with increasing $B_{\parallel }$ up to 9 T, and then strengthens on further increasing $B_{\parallel }$, which also restores the $2e^2/h$ plateau. Our results are consistent with spin-incoherent transport in a one-dimensional wire.