Centre de Nanosciences et de Nanotechnologies (C2N), CNRS, Université Paris Sud-Université Paris-Saclay, Université Paris Diderot-Sorbonne Paris Cité, 91120 Palaiseau, France.
Institute for Theoretical Physics, ETH Zurich, CH-8093 Zurich, Switzerland.
Nature. 2016 Aug 4;536(7614):58-62. doi: 10.1038/nature19072.
In 1909, Millikan showed that the charge of electrically isolated systems is quantized in units of the elementary electron charge e. Today, the persistence of charge quantization in small, weakly connected conductors allows for circuits in which single electrons are manipulated, with applications in, for example, metrology, detectors and thermometry. However, as the connection strength is increased, the discreteness of charge is progressively reduced by quantum fluctuations. Here we report the full quantum control and characterization of charge quantization. By using semiconductor-based tunable elemental conduction channels to connect a micrometre-scale metallic island to a circuit, we explore the complete evolution of charge quantization while scanning the entire range of connection strengths, from a very weak (tunnel) to a perfect (ballistic) contact. We observe, when approaching the ballistic limit, that charge quantization is destroyed by quantum fluctuations, and scales as the square root of the residual probability for an electron to be reflected across the quantum channel; this scaling also applies beyond the different regimes of connection strength currently accessible to theory. At increased temperatures, the thermal fluctuations result in an exponential suppression of charge quantization and in a universal square-root scaling, valid for all connection strengths, in agreement with expectations. Besides being pertinent for the improvement of single-electron circuits and their applications, and for the metal-semiconductor hybrids relevant to topological quantum computing, knowledge of the quantum laws of electricity will be essential for the quantum engineering of future nanoelectronic devices.
1909 年，密立根（Millikan）表明，电隔离系统的电荷是电子基本电荷 e 的整数倍。如今，在小型、弱连接导体中电荷量子化的持续存在允许进行单电子操纵的电路，例如在计量学、探测器和温度计等领域应用。然而，随着连接强度的增加，电荷的离散性会逐渐被量子涨落所削弱。在这里，我们报告了电荷量子化的完整量子控制和特性。通过使用基于半导体的可调谐元素传导通道将微尺度金属岛与电路连接，我们在扫描整个连接强度范围时探索了电荷量子化的完全演化，从非常弱（隧道）到完美（弹道）接触。我们观察到，当接近弹道极限时，电荷量子化被量子涨落破坏，并按剩余电子穿过量子通道被反射的概率的平方根进行缩放；这种缩放也适用于理论目前无法企及的不同连接强度范围。在较高温度下，热涨落导致电荷量子化呈指数衰减，并呈普遍的平方根缩放，适用于所有连接强度，这与预期一致。除了对改进单电子电路及其应用以及对与拓扑量子计算相关的金属半导体混合体有重要意义外，了解电的量子定律对于未来纳米电子器件的量子工程至关重要。
