Wei Di S, van der Sar Toeno, Sanchez-Yamagishi Javier D, Watanabe Kenji, Taniguchi Takashi, Jarillo-Herrero Pablo, Halperin Bertrand I, Yacoby Amir
John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138, USA.
Department of Physics, Harvard University, Cambridge, MA 02138, USA.
Sci Adv. 2017 Aug 18;3(8):e1700600. doi: 10.1126/sciadv.1700600. eCollection 2017 Aug.
Confined to a two-dimensional plane, electrons in a strong magnetic field travel along the edge in one-dimensional quantum Hall channels that are protected against backscattering. These channels can be used as solid-state analogs of monochromatic beams of light, providing a unique platform for studying electron interference. Electron interferometry is regarded as one of the most promising routes for studying fractional and non-Abelian statistics and quantum entanglement via two-particle interference. However, creating an edge-channel interferometer in which electron-electron interactions play an important role requires a clean system and long phase coherence lengths. We realize electronic Mach-Zehnder interferometers with record visibilities of up to 98% using spin- and valley-polarized edge channels that copropagate along a pn junction in graphene. We find that interchannel scattering between same-spin edge channels along the physical graphene edge can be used to form beamsplitters, whereas the absence of interchannel scattering along gate-defined interfaces can be used to form isolated interferometer arms. Surprisingly, our interferometer is robust to dephasing effects at energies an order of magnitude larger than those observed in pioneering experiments on GaAs/AlGaAs quantum wells. Our results shed light on the nature of edge-channel equilibration and open up new possibilities for studying exotic electron statistics and quantum phenomena.
在强磁场中，限制在二维平面内的电子沿着边缘在一维量子霍尔通道中传播，这些通道可防止背散射。这些通道可用作单色光束的固态类似物，为研究电子干涉提供了一个独特的平台。电子干涉测量法被认为是通过双粒子干涉研究分数统计和非阿贝尔统计以及量子纠缠最有前途的途径之一。然而，创建一个电子 - 电子相互作用起重要作用的边缘通道干涉仪需要一个干净的系统和长的相位相干长度。我们利用沿石墨烯中的 pn 结共传播的自旋和谷极化边缘通道，实现了可见度高达 98%的创纪录的电子马赫 - 曾德尔干涉仪。我们发现，沿着物理石墨烯边缘的同自旋边缘通道之间的通道间散射可用于形成分束器，而沿着栅极定义界面不存在通道间散射可用于形成孤立的干涉仪臂。令人惊讶的是，我们的干涉仪对于能量比在 GaAs/AlGaAs 量子阱的开创性实验中观察到的能量大一个数量级的退相效应具有鲁棒性。我们的结果揭示了边缘通道平衡的本质，并为研究奇异电子统计和量子现象开辟了新的可能性。
