Semiconductor nanowires with strong Rashba spin-orbit coupling are currently on the spotlight of several research fields such as spintronics, topological materials and quantum computation. While most theoretical models assume an infinitely long nanowire, in actual experimental setups the nanowire has a finite length, is contacted to metallic electrodes and is partly covered by gates. By taking these effects into account through an inhomogeneous spin-orbit coupling profile, we show that in general two types of bound states arise in the nanowire, namely confinement bound states and interface bound states. The appearance of confinement bound states, related to the finite length of the nanowire, is favoured by a mismatch of the bulk band bottoms characterizing the lead and the nanowire, and occurs even in the absence of magnetic field. In contrast, an interface bound states may only appear if a magnetic field applied perpendicularly to the spin-orbit field direction overcomes a critical value, and is favoured by an alignment of the band bottoms of the two regions across the interface. We describe in details the emergence of these two types of bound states, pointing out their differences. Furthermore, we show that when a nanowire portion is covered by a gate the application of a magnetic field can change the nature of the electronic ground state from a confinement to an interface bound state, determining a redistribution of the electron charge.

中文翻译：

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自旋轨道耦合纳米线的约束与界面结合态

具有强Rashba自旋-轨道耦合的半导体纳米线目前是自旋电子学，拓扑材料和量子计算等多个研究领域的关注焦点。尽管大多数理论模型都假定纳米线无限长，但在实际实验设置中，纳米线具有有限的长度，与金属电极接触，并且部分被栅极覆盖。通过考虑非均匀自旋轨道耦合分布的这些影响，我们表明，纳米线通常会出现两种类型的键合状态，即约束键合状态和界面键合状态。与纳米线的有限长度有关的限制束缚态的出现受到表征引线和纳米线的体带底部不匹配的影响，甚至在没有磁场的情况下也会发生。相反，仅当垂直于自旋轨道场方向施加的磁场超过临界值，并且界面两端的两个区域的带底对齐时，界面约束状态才会出现。我们详细描述了这两种类型的结合状态的出现，并指出了它们的区别。此外，我们表明，当纳米线部分被栅极覆盖时，施加磁场可以将电子基态的性质从限制状态更改为界面结合状态，从而确定电子电荷的重新分布。我们详细描述了这两种类型的结合状态的出现，并指出了它们的区别。此外，我们表明，当纳米线部分被栅极覆盖时，施加磁场可以将电子基态的性质从限制状态更改为界面结合状态，从而确定电子电荷的重新分布。我们详细描述了这两种类型的结合状态的出现，并指出了它们的区别。此外，我们表明，当纳米线部分被栅极覆盖时，施加磁场可以将电子基态的性质从限制状态更改为界面结合状态，从而确定电子电荷的重新分布。