Zhu Zheyi, Kim Stephan, Lei Shiming, Schoop Leslie M, Cava R J, Ong N P
Department of Physics, Princeton University, Princeton, NJ 08544.
Department of Electrical and Computer Engineering, Princeton University, Princeton, NJ 08544.
Proc Natl Acad Sci U S A. 2022 Jul 12;119(28):e2204468119. doi: 10.1073/pnas.2204468119. Epub 2022 Jul 8.
When an electron is incident on a superconductor from a metal, it is reflected as a hole in a process called Andreev reflection. If the metal is sandwiched between two superconductors in an junction, multiple Andreev reflections (MARs) occur. We have found that, in junctions with high transparency ([Formula: see text]) based on the Dirac semimetal MoTe, the MAR features are observed with exceptional resolution. By tuning the phase difference [Formula: see text] between the bracketing Al superconductors, we establish that the MARs coexist with a Josephson supercurrent [Formula: see text]. As we vary the junction voltage , the supercurrent amplitude [Formula: see text] varies in step with the MAR order , revealing a direct relation between them. Two successive Andreev reflections serve to shuttle a Cooper pair across the junction. If the pair is shuttled coherently, it contributes to [Formula: see text]. The experiment measures the fraction of pairs shuttled coherently vs. . Surprisingly, superconductivity in MoTe does not affect the MAR features.
当一个电子从金属入射到超导体上时，在一个称为安德列夫反射的过程中它会被反射为一个空穴。如果该金属夹在一个结中的两个超导体之间，就会发生多次安德列夫反射（MARs）。我们发现，在基于狄拉克半金属碲化钼（MoTe）的具有高透明度（[公式：见正文]）的结中，能以极高的分辨率观察到MAR特征。通过调节两侧铝超导体之间的相位差[公式：见正文]，我们确定MARs与约瑟夫森超电流[公式：见正文]共存。当我们改变结电压时，超电流幅度[公式：见正文]随MAR阶数同步变化，揭示了它们之间的直接关系。两次连续的安德列夫反射用于将一个库珀对穿过结。如果该对是相干传输的，它会对[公式：见正文]有贡献。该实验测量了相干传输的对的比例与[具体变量]的关系。令人惊讶的是，碲化钼中的超导性并不影响MAR特征。
