Spin-Splitting Transport in Narrow-Gap Heterojunction Narrow Wires

We systematically studied spin-orbit (SO) interaction in narrow wires with a variety of widths, using two different approaches. Etched wires were used in the first approach, while side-gate wires were used in the second. To determine the SO coupling constant, α, we measured magneto-resistances at 1.6 K. α remained almost constant for the etched wires with a width wider than 0.4 μm. On the other hand in the side-gate wires, α increased with decreasing wire width from 2 μm down to about 1 μm with the application of asymmetric side-gate voltage. The increase of α observed in the side-gate wire could be attributed to the enhanced total asymmetric electric field, Easym, total, which is the vector sum of the vertical electric field EV originally existing at the hetero-interface and the horizontal electric field EH resulting from the side-gate voltage application. A rough estimation of α based on this assumption was made and compared with the experimental results.