趋近宏观长度的量子线中的离散态与弹道干涉
Discrete states and ballistic interference in quantum wires approaching macroscopic lengths
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中文总结 AI 辅助
该研究制备出长度达18μm、纵横比近1000的理想一维量子线，通过低温低噪声测量系统观测到离散量子态与弹道量子干涉，验证了单粒子薛定谔量子力学在趋近宏观尺寸系统中的适用性。
中文摘要 AI 辅助
增大展现量子效应的系统尺寸是一项艰巨任务，其限制因素包括退相干、量子能级间距的减小，以及尺寸增长时破坏量子行为的无序效应。一维系统在横向方向具有极强的束缚，因此通常会增强量子效应，但众所周知其对无序极为敏感。本研究中，我们展示了一种一维电子系统，其具有离散量子能级和完全弹道相干量子干涉，长度可达18μm。对带有中央门控段的两条平行量子线进行的隧穿光谱测量显示，其呈现出复杂的干涉图案，在磁场和密度下表现出多种不同的周期。对三种不同线长的分析，以及与无任何自由参数的单粒子数值模拟的对比，成功解释了包括观测到的周期在内的完整图案。因此，这些线是纵横比接近1000的本质上理想的一维系统。此外，在低偏压下，我们不仅观测到了库仑充电能，还能在长达10μm的量子线中，当中央门填充100个电子时，清晰分辨出离散的轨道和自旋态，这得益于最先进的低温低噪声测量系统。自旋填充序列完全规则，严格交替自旋向上和自旋向下，避免了高自旋态，而峰电导则根据前述干涉图案进行调制。这些显著结果表明，在合适条件下，长达18μm的系统中可观测到弹道量子干涉和离散量子态等单粒子薛定谔量子力学现象，从而趋近宏观尺寸。
英文摘要
Increasing the size of a system showing quantum effects is a difficult task limited by decoherence, a diminishing quantum level spacing, and the effects of disorder spoiling the quantum behavior when growing in size. Systems in 1D offer very strong confinement in the transverse directions, thus generally enhancing quantum effects, but are notoriously sensitive to disorder. In this work, we present a system of 1D electrons exhibiting discrete quantum levels and fully ballistic coherent quantum interference with lengths of up to 18\,$μ$m. Tunneling spectroscopy between two parallel quantum wires with a central gated segment shows intricate interference patterns exhibiting several different periods in magnetic field and density. An analysis over three different wire lengths and a comparison with single particle numerical simulations without any free parameters remarkably explains the full pattern including the observed periods. Therefore, these wires are essentially ideal 1D systems with aspect ratios approaching 1'000. In addition, at low bias, we also observe not only the Coulomb charging energies but can clearly resolve the discrete orbital and spin states in up to 10\,$μ$m long wires when filling 100 electrons with the center gate. This is made visible by a state-of-the-art low temperature and low noise measurement system. The spin filling sequence is completely regular, strictly alternating spin up and down, avoiding high spin states, while the peak conductance is modulated in accordance with the previously discussed interference patterns. These striking results show that single particle Schrödinger quantum mechanics such as ballistic quantum interference and discrete quantum states may be observed, under the right conditions, in systems of up to 18\,$μ$m length, thus approaching macroscopic sizes.
