Univ. Grenoble Alpes, Institut Néel, F-38000 Grenoble, France.
CNRS, Institut Néel, F-38000 Grenoble, France.
Nat Commun. 2017 Apr 13;8:14983. doi: 10.1038/ncomms14983.
Charge carriers in the quantum Hall regime propagate via one-dimensional conducting channels that form along the edges of a two-dimensional electron gas. Controlling their transmission through a gate-tunable constriction, also called quantum point contact, is fundamental for many coherent transport experiments. However, in graphene, tailoring a constriction with electrostatic gates remains challenging due to the formation of p-n junctions below gate electrodes along which electron and hole edge channels co-propagate and mix, short circuiting the constriction. Here we show that this electron-hole mixing is drastically reduced in high-mobility graphene van der Waals heterostructures thanks to the full degeneracy lifting of the Landau levels, enabling quantum point contact operation with full channel pinch-off. We demonstrate gate-tunable selective transmission of integer and fractional quantum Hall edge channels through the quantum point contact. This gate control of edge channels opens the door to quantum Hall interferometry and electron quantum optics experiments in the integer and fractional quantum Hall regimes of graphene.
在量子霍尔效应 regime 中，电荷载流子通过沿着二维电子气边缘形成的一维导电通道传播。通过门可调缩颈（也称为量子点接触）控制它们的传输，对于许多相干输运实验来说是至关重要的。然而，在石墨烯中，由于在栅极电极下方形成 p-n 结，静电门控缩颈的制作仍然具有挑战性，在 p-n 结中，电子和空穴边缘通道共同传播并混合，从而使缩颈短路。在这里，我们表明，由于 Landau 能级的完全简并消除，在高迁移率石墨烯范德华异质结构中，这种电子-空穴混合大大减少，从而实现了具有完全通道夹断的量子点接触操作。我们通过量子点接触演示了整数和分数量子霍尔边缘通道的门控可调选择性传输。这种对边缘通道的门控为在石墨烯的整数和分数量子霍尔区进行量子霍尔干涉测量和电子量子光学实验打开了大门。
