Academy for Advanced Interdisciplinary Studies, Peking University, Beijing 100871, China.
State Key Laboratory for Mesoscopic Physics, School of Physics, Peking University, Beijing 100871, China.
Phys Rev Lett. 2018 Dec 7;121(23):237701. doi: 10.1103/PhysRevLett.121.237701.
The combination of superconductivity and surface states in Dirac semimetal can produce a 4π-periodic supercurrent in a Josephson junction configuration, which can be revealed by the missing of odd Shapiro steps (especially the n=1 step). However, the suppression of the n=1 step is also anticipated in the high-power oscillatory regime of the ordinary 2π-periodic Josephson effect, which is irrelevant to the 4π-periodic supercurrent. Here, in order to identify the origin of the suppressed n=1 step, we perform the measurements of radio frequency irradiation on Nb-Dirac semimetal Cd_{3}As_{2} nanowire-Nb junctions with continuous power dependence at various frequencies. Besides the n=1 step suppression, we uncover a residual supercurrent of first node at the n=0 step, which provides a direct and predominant signature of the 4π-periodic supercurrent. Furthermore, by tuning the gate voltage, we can modulate the surface and bulk state contribution and the visibility of the n=1 step. Our results provide deep insights to explore the topological superconductivity in Dirac semimetals.
在狄拉克半金属中，超导性和表面态的结合可以在约瑟夫森结结构中产生一个 4π 周期的超导电流，这可以通过缺失奇数 Shapiro 台阶（特别是 n=1 台阶）来揭示。然而，在普通的 2π 周期约瑟夫森效应的高功率振荡状态下，n=1 台阶也会被抑制，这与 4π 周期超导电流无关。在这里，为了确定被抑制的 n=1 台阶的来源，我们在各种频率下对具有连续功率依赖性的 Nb-狄拉克半金属 Cd_{3}As_{2}纳米线-Nb 结进行了射频辐照测量。除了 n=1 台阶抑制之外，我们还在 n=0 台阶处发现了第一节点的残余超导电流，这为 4π 周期超导电流提供了一个直接且主要的特征。此外，通过调节栅极电压，我们可以调制表面和体状态的贡献以及 n=1 台阶的可见度。我们的结果为探索狄拉克半金属中的拓扑超导性提供了深入的见解。
