Kumada N, Parmentier F D, Hibino H, Glattli D C, Roulleau P
NTT Basic Research Laboratories, NTT Corporation, 3-1 Morinosato-Wakamiya, Atsugi 243-0198, Japan.
Nanoelectronics Group, Service de Physique de l'Etat Condensé, IRAMIS/DSM (CNRS URA 2464), CEA Saclay, F-91191 Gif-sur-Yvette, France.
Nat Commun. 2015 Sep 4;6:8068. doi: 10.1038/ncomms9068.
Graphene offers a unique system to investigate transport of Dirac Fermions at p-n junctions. In a magnetic field, combination of quantum Hall physics and the characteristic transport across p-n junctions leads to a fractionally quantized conductance associated with the mixing of electron-like and hole-like modes and their subsequent partitioning. The mixing and partitioning suggest that a p-n junction could be used as an electronic beam splitter. Here we report the shot noise study of the mode-mixing process and demonstrate the crucial role of the p-n junction length. For short p-n junctions, the amplitude of the noise is consistent with an electronic beam-splitter behaviour, whereas, for longer p-n junctions, it is reduced by the energy relaxation. Remarkably, the relaxation length is much larger than typical size of mesoscopic devices, encouraging using graphene for electron quantum optics and quantum information processing.
石墨烯提供了一个独特的系统，用于研究狄拉克费米子在 p-n 结处的输运。在磁场中，量子霍尔物理与跨越 p-n 结的特征输运相结合，导致与类电子和类空穴模式的混合及其后续分配相关的分数化量子化电导。这种混合和分配表明 p-n 结可以用作电子分束器。在此，我们报告了对模式混合过程的散粒噪声研究，并证明了 p-n 结长度的关键作用。对于短 p-n 结，噪声幅度与电子分束器行为一致，而对于较长的 p-n 结，它会因能量弛豫而降低。值得注意的是，弛豫长度比介观器件的典型尺寸大得多，这促使人们将石墨烯用于电子量子光学和量子信息处理。
