Wang He, Wang Huichao, Chen Yuqin, Luo Jiawei, Yuan Zhujun, Liu Jun, Wang Yong, Jia Shuang, Liu Xiong-Jun, Wei Jian, Wang Jian
International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China; Collaborative Innovation Center of Quantum Matter, Beijing, China.
Center of Electron Microscopy, State Key Laboratory of Silicon Materials, School of Materials Science and Engineering, Zhejiang University, Hangzhou 310027, China.
Sci Bull (Beijing). 2017 Mar 30;62(6):425-430. doi: 10.1016/j.scib.2017.02.009. Epub 2017 Feb 24.
Weyl fermion is a massless Dirac fermion with definite chirality, which has been long pursued since 1929. Though it has not been observed as a fundamental particle in nature, Weyl fermion can be realized as low-energy excitation around Weyl point in Weyl semimetal, which possesses Weyl fermion cones in the bulk and nontrivial Fermi arc states on the surface. As a firstly discovered Weyl semimetal, TaAs crystal possesses 12 pairs of Weyl points in the momentum space, which are topologically protected against small perturbations. Here, we report for the first time the tip induced superconductivity on TaAs crystal by point contact spectroscopy. The zero bias conductance peak as well as a conductance plateau with double conductance peaks and sharp double dips are observed in the point contact spectra simultaneously, indicating unconventional superconductivity. Our further theoretical study suggests that the induced superconductivity may have nontrivial topology. The present work opens a new route in investigating the novel superconducting states based on Weyl materials.
外尔费米子是一种具有确定手性的无质量狄拉克费米子，自1929年以来一直备受追寻。尽管它尚未作为一种基本粒子在自然界中被观测到，但外尔费米子可以在 Weyl 半金属的外尔点周围被实现为低能激发，这种材料在体态中具有外尔费米子锥，在表面具有非平凡的费米弧态。作为首个被发现的Weyl半金属，TaAs晶体在动量空间中拥有12对外尔点，这些点在拓扑上受到保护，免受小扰动的影响。在此，我们首次通过点接触光谱法报道了在TaAs晶体上由针尖诱导的超导性。在点接触光谱中同时观测到零偏置电导峰以及具有双电导峰和尖锐双凹陷的电导平台，这表明存在非常规超导性。我们进一步的理论研究表明，诱导的超导性可能具有非平凡拓扑结构。目前的工作为研究基于外尔材料的新型超导态开辟了一条新途径。
