Interaction Effects at Crossings of Spin-Polarized One-Dimensional Subbands

Abstract

We report conductance measurements of ballistic one-dimensional (1D) wires defined in GaAs/AlGaAs heterostructures in an in-plane magnetic field, $B$. When the Zeeman energy is equal to the 1D subband energy spacing, the spin-split subband $N\uparrow$ intersects $(N+1)\downarrow$, where $N$ is the index of the spin-degenerate 1D subband. At the crossing of $N=1\uparrow$ and $N=2\downarrow$ subbands, there is a spontaneous splitting giving rise to an additional conductance structure evolving from the $1.5(2e^2/h)$ plateau. With further increase in $B$, the structure develops into a plateau and lowers to $2e^2/h$. With increasing temperature and magnetic field the structure shows characteristics of the 0.7 structure. Our results suggest that at low densities a spontaneous spin splitting occurs whenever two 1D subbands of opposite spins cross.