Department of Physics, Pohang University of Science and Technology, Pohang, 790-784, Republic of Korea.
Advanced Materials Laboratory, National Institute for Materials Science, 1-1 Namiki, Tsukuba, 305-0044, Japan.
Sci Rep. 2017 Sep 8;7(1):10953. doi: 10.1038/s41598-017-11209-w.
Recently, there has been significant interest in superconducting coherence via chiral quantum-Hall (QH) edge channels at an interface between a two-dimensional normal conductor and a superconductor (N-S) in a strong transverse magnetic field. In the field range where the superconductivity and the QH state coexist, the coherent confinement of electron- and hole-like quasiparticles by the interplay of Andreev reflection and the QH effect leads to the formation of Andreev edge states (AES) along the N-S interface. Here, we report the electrical conductance characteristics via the AES formed in graphene-superconductor hybrid systems in a three-terminal configuration. This measurement configuration, involving the QH edge states outside a graphene-S interface, allows the detection of the longitudinal and QH conductance separately, excluding the bulk contribution. Convincing evidence for the superconducting coherence and its propagation via the chiral QH edge channels is provided by the conductance enhancement on both the upstream and the downstream sides of the superconducting electrode as well as in bias spectroscopy results below the superconducting critical temperature. Propagation of superconducting coherence via QH edge states was more evident as more edge channels participate in the Andreev process for high filling factors with reduced valley-mixing scattering.
最近，人们对在二维正常导体和超导体（N-S）之间的界面上通过手性量子霍尔（QH）边缘通道的超导相干性产生了浓厚的兴趣，在该界面上存在强横向磁场。在超导性和 QH 态共存的磁场范围内，电子和空穴类准粒子的相干限制通过安德烈夫反射和 QH 效应的相互作用导致在 N-S 界面沿线形成安德烈夫边缘态（AES）。在这里，我们报告了在三端配置的石墨烯-超导混合系统中通过 AES 形成的电导特性。这种测量配置涉及到石墨烯-S 界面外部的 QH 边缘态，可以分别检测纵向和 QH 电导，排除了体贡献。超导相干性及其通过手性 QH 边缘通道传播的令人信服的证据是通过超导电极的上下游两侧的电导增强以及在超导临界温度以下的偏压光谱结果提供的。随着更多的边缘通道参与安德烈夫过程，对于具有减少的谷混合散射的高填充因子，超导相干性通过 QH 边缘态的传播变得更加明显。
