Physikalisches Institut, EP3, University of Würzburg, Am Hubland, D-97074 Würzburg, Germany.
Phys Rev Lett. 2012 Nov 2;109(18):186806. doi: 10.1103/PhysRevLett.109.186806.
A strained and undoped HgTe layer is a three-dimensional topological insulator, in which electronic transport occurs dominantly through its surface states. In this Letter, we present transport measurements on HgTe-based Josephson junctions with Nb as a superconductor. Although the Nb-HgTe interfaces have a low transparency, we observe a strong zero-bias anomaly in the differential resistance measurements. This anomaly originates from proximity-induced superconductivity in the HgTe surface states. In the most transparent junction, we observe periodic oscillations of the differential resistance as a function of an applied magnetic field, which correspond to a Fraunhofer-like pattern. This unambiguously shows that a precursor of the Josephson effect occurs in the topological surface states of HgTe.
拉伸且未掺杂的 HgTe 层是一种三维拓扑绝缘体，其中电子输运主要通过其表面态进行。在这篇快报中，我们展示了基于 HgTe 的约瑟夫森结的输运测量结果，其中 Nb 为超导体。尽管 Nb-HgTe 界面的透明度较低，但我们在差分电阻测量中观察到了一个很强的零偏压异常。该异常源于 HgTe 表面态中诱导的超导性。在最透明的结中，我们观察到差分电阻作为外加磁场函数的周期性振荡，这对应于夫琅禾费图案。这明确表明约瑟夫森效应的前体出现在 HgTe 的拓扑表面态中。
